Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 03, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Trading Symbol	TTOO
Entity Registrant Name	T2 Biosystems, Inc.
Entity Central Index Key	0001492674
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		36,019,883

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 29,733	$ 41,799
Accounts receivable	582	467
Prepaid expenses and other current assets	626	708
Inventories	2,082	1,344
Total current assets	33,023	44,318
Property and equipment, net	8,710	10,015
Restricted cash	180	260
Other assets	206	268
Total assets	42,119	54,861
Current liabilities:
Accounts payable	779	648
Accrued expenses and other current liabilities	5,606	6,218
Derivative liability	2,096	2,238
Notes payable	41,303	40,696
Deferred revenue	887	1,736
Current portion of lease incentives	251	246
Total current liabilities	50,922	51,782
Notes payable, net of current portion	609	1,008
Lease incentives, net of current portion	675	731
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding at March 31, 2018 and December 31, 2017
Common stock, $0.001 par value; 200,000,000 shares authorized; 36,019,883 and 35,948,900 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	36	36
Additional paid-in capital	268,807	267,421
Accumulated deficit	(278,930)	(266,117)
Total stockholders’ (deficit) equity	(10,087)	1,340
Total liabilities and stockholders’ equity	$ 42,119	$ 54,861

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	36,019,883	35,948,900
Common stock, shares outstanding	36,019,883	35,948,900

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Product revenue	$ 1,048	$ 631
Research revenue	1,263	310
Total revenue	2,311	941
Costs and expenses:
Cost of product revenue	3,273	1,627
Research and development	4,718	6,585
Selling, general and administrative	5,755	5,874
Total costs and expenses	13,746	14,086
Loss from operations	(11,435)	(13,145)
Interest expense, net	(1,568)	(1,637)
Other income, net	90	79
Net loss and comprehensive loss	$ (12,913)	$ (14,703)
Net loss per share — basic and diluted	$ (0.36)	$ (0.48)
Weighted-average number of common shares used in computing net loss per share — basic and diluted	35,978,306	30,531,180

Condensed Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net loss	$ (12,913)	$ (14,703)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	629	694
Stock-based compensation expense	1,381	1,157
Change in fair value of derivative instrument	(142)
Non-cash interest expense	560	639
Deferred rent	(52)	(53)
Changes in operating assets and liabilities:
Accounts receivable	(115)	(82)
Prepaid expenses and other assets	145	(111)
Inventories	64	314
Accounts payable	132	199
Accrued expenses and other liabilities	(682)	(494)
Deferred revenue	(749)	(318)
Net cash used in operating activities	(11,742)	(12,758)
Cash flows from investing activities
Purchases and manufacture of property and equipment	(56)	(1,594)
Net cash used in investing activities	(56)	(1,594)
Cash flows from financing activities
Proceeds from issuance of common stock and stock options exercises, net	4	339
Payments of issuance costs for notes payable		(354)
Repayments of note payable	(352)	(299)
Net cash used in financing activities	(348)	(314)
Net decrease in cash, cash equivalents and restricted cash	(12,146)	(14,666)
Cash, cash equivalents and restricted cash at beginning of period	42,059	73,748
Cash, cash equivalents and restricted cash at end of period	29,913	59,082
Supplemental disclosures of cash flow information
Cash paid for interest	972	993
Supplemental disclosures of noncash activities
Transfer of T2 owned instruments and components to inventory	802	0
Accrued property and equipment	$ 119	$ 61

Nature of Business	3 Months Ended
Nature of Business	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	1. Nature of Business T2 Biosystems, Inc. (the “Company”) was incorporated on April 27, 2006 as a Delaware corporation with operations based in Lexington, Massachusetts. The Company is an in vitro diagnostics company that has developed an innovative and proprietary technology platform that offers a rapid, sensitive and simple alternative to existing diagnostic methodologies. The Company is using its T2 Magnetic Resonance technology (“T2MR”) to develop a broad set of applications aimed at lowering mortality rates, improving patient outcomes and reducing the cost of healthcare by helping medical professionals make targeted treatment decisions earlier. T2MR enables rapid detection of pathogens, biomarkers and other abnormalities in a variety of unpurified patient sample types, including whole blood, plasma, serum, saliva, sputum and urine, and can detect cellular targets at limits of detection as low as one colony forming unit per milliliter (“CFU/mL”). The Company’s initial development efforts target sepsis and Lyme disease, which are areas of significant unmet medical need in which existing therapies could be more effective with improved diagnostics. On September 22, 2014, the Company received market clearance from the U.S. Food and Drug Administration (“FDA”) for its first two products, the T2Dx Instrument (the “T2Dx”) and T2Candida Panel (“T2Candida”). On June 30, 2017 the Company received a CE Mark for its T2Bacteria Panel (“T2Bacteria”). On September 8, 2017 the Company filed a 510(k) premarket submission for the T2Bacteria Panel with the FDA. The Company has devoted substantially all of its efforts to research and development, business planning, recruiting management and technical staff, acquiring operating assets, raising capital, and, most recently, the commercialization and improvement of its existing products. Liquidity and Going Concern At March 31, 2018, the Company had cash and cash equivalents of $29.7 million and an accumulated deficit of $278.9 million. The future success of the Company is dependent on its ability to successfully commercialize its products, obtain regulatory clearance for and successfully launch its future product candidates, obtain additional capital and ultimately attain profitable operations. Historically, the Company has funded its operations primarily through its August 2014 initial public offering, its December 2015 confidentially marketed public offering (“CMPO”), its September 2016 private investment in public equity (“PIPE”) financing, its September 2017 CMPO, private placements of redeemable convertible preferred stock and through debt financing arrangements. The Company is subject to a number of risks similar to other newly commercial life science companies, including, but not limited to commercially launching the Company’s products, development and market acceptance of the Company’s product candidates, development by its competitors of new technological innovations, protection of proprietary technology, and raising additional capital. Having obtained authorization from the FDA to market T2Dx and T2Candida, the Company has incurred significant commercialization expenses related to product sales, marketing, manufacturing and distribution. The Company may seek to fund its operations through public equity or private equity or debt financings, as well as other sources. However, the Company may be unable to raise additional funds or enter into such other arrangements when needed, on favorable terms, or at all. The Company’s failure to raise capital or enter into such other arrangements if and when needed would have a negative impact on the Company’s business, results of operations and financial condition and the Company’s ability to develop and commercialize T2Dx, T2Candida, T2Bacteria and other product candidates. Pursuant to the requirements of Accounting Standards Codification (ASC) 205-40, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern, management must evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the Company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. Management believes that its existing cash and cash equivalents at March 31, 2018, together with funding available under the Term Loan Agreement (as defined below), will be sufficient to allow the Company to fund its current operating plan through March 31, 2019. However, as certain elements of the Company’s operating plan are outside of the Company’s control, including the approval of the Company’s T2Bacteria Panel and receipt of certain development and regulatory milestone payments under the Company’s Co-Development agreements, they cannot be considered probable. Under ASC 205-40, the future receipt of potential funding from the Company’s Co-Development partners and other resources cannot be considered probable at this time because none of the plans are entirely within the Company’s control. In addition, the Company is required to maintain a minimum cash balance under its Term Loan Agreement with CRG Servicing LLC (“CRG”) (Note 6). These conditions raise substantial doubt regarding the Company’s ability to continue as a going concern for a period of one year after the date that the financial statements are issued. Management’s plans to alleviate the conditions that raise substantial doubt include raising additional funding, earning milestone payments pursuant to the Company’s Co-Development agreements, delaying certain research projects and capital expenditures and eliminating certain future operating expenses in order to fund operations at reduced levels for the Company to continue as a going concern for a period of 12 months from the date the financial statements are issued. Management has concluded the likelihood that its plan to obtain sufficient funding from one or more of these sources or adequately reduce expenditures will be successful, while reasonably possible, is less than probable. Accordingly, the Company has concluded that substantial doubt exists about the Company’s ability to continue as a going concern for a period of at least twelve months from the date of issuance of these consolidated financial statements. The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above. For more information, refer to the section titled “Liquidity and Capital Resources” in Item 2, Management’s Discussion and Analysis of Financial Condition and Results of Operations and the section entitled “Risk Factors” in the Annual Report on Form 10-K for the year ended December 31, 2017, for additional risks associated with our capital needs.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The Company’s financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States GAAP as defined in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, T2 Biosystems Securities Corporation. All intercompany balances and transactions have been eliminated.

We have evaluated subsequent events from March 31, 2018 through the date of the issuance of these condensed consolidated financial statements and have determined that no material subsequent events have occurred that would have a material effect on the information presented in these consolidated financial statements.

Unaudited Interim Financial Information

Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. Accordingly, these interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

The accompanying interim condensed consolidated balance sheet as of March 31, 2018, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2018 and 2017, the condensed consolidated statements of cash flows for the three months ended March 31, 2018 and 2017 and the related financial data and other information disclosed in these notes are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements, and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2018, and the results of its operations and its cash flows for the three months ended March 31, 2018 and 2017. The results for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018, any other interim periods, or any future year or period.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company views its operations and manages its business in one operating segment, which is the business of developing and, upon regulatory clearance, commercializing its diagnostic products aimed at lowering mortality rates, improving patient outcomes and reducing the cost of healthcare by helping medical professionals make targeted treatment decisions earlier.

Net Loss Per Share

Basic net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting the weighted-average number of shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the diluted net loss per share calculation, stock options and unvested restricted stock are considered to be common stock equivalents, but have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share applicable to common stockholders was the same for all periods presented.

Guarantees

As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while each such officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification is the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ liability insurance coverage that limits its exposure and enables the Company to recover a portion of any future amounts paid.

The Company leases office, laboratory and manufacturing space under noncancelable operating leases. The Company has standard indemnification arrangements under the leases that require it to indemnify the landlords against all costs, expenses, fines, suits, claims, demands, liabilities, and actions directly resulting from any breach, violation or nonperformance of any covenant or condition of the Company’s leases.

In the ordinary course of business, the Company enters into indemnification agreements with certain suppliers and business partners where the Company has certain indemnification obligations limited to the costs, expenses, fines, suits, claims, demands, liabilities and actions directly resulting from the Company’s gross negligence or willful misconduct, and in certain instances, breaches, violations or nonperformance of covenants or conditions under the agreements.

As of March 31, 2018 and December 31, 2017, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.

Revenue Recognition

The Company adopted ASC 606, Revenue from Contracts with Customers (“ASC 606”) on January 1, 2018 using the modified retrospective method for all contracts not completed as of the date of adoption. For contracts that were modified before the effective date, the Company reflected the aggregate effect of all modifications when identifying performance obligations and allocating transaction price in accordance with practical expedient ASC 606-10-65-1-(f)-4. The reported results for 2018 reflect the application of ASC 606 guidance while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition (“ASC 605” or "legacy GAAP"). The impact of ASC 606 as of, and for the three months ended, March 31, 2018 was not material to the condensed consolidated financial statements.

The Company generates revenue from product sales, the sale of instruments, consumable diagnostic tests, related services, reagent rental agreements and research and development agreements with third parties. Pursuant to ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration the Company expects to be entitled to receive in exchange for these goods and services.

Once a contract is determined to be within the scope of ASC 606 at contract inception, the Company reviews the contract to determine which performance obligations the Company must deliver and which of these performance obligations are distinct. The Company recognizes as revenues the amount of the transaction price that is allocated to the respective performance obligation when the performance obligation is satisfied or as it is satisfied. Generally, the Company's performance obligations are transferred to customers at a point in time, typically upon shipment, or over time, as services are performed.


Most of the Company’s contracts with customers contain multiple performance obligations. For these contracts, the Company accounts for individual performance obligations separately if they are distinct. The transaction price is allocated to the separate performance obligations on a relative standalone selling price basis.

Product revenue is generated by the sale of instruments and consumable diagnostic tests predominantly through the Company’s direct sales force in the United States and distributors in geographic regions outside the United States. The Company does not offer product return or exchange rights (other than those relating to defective goods under warranty) or price protection allowances to its customers, including its distributors. Payment terms granted to distributors are the same as those granted to end-user customers and payments are not dependent upon the distributors’ receipt of payment from their end-user customers. The Company either sells instruments to customers and international distributors, or retains title and places the instrument at the customer site pursuant to a reagent rental agreement. When an instrument is purchased by a customer, the Company recognizes revenue when the related performance obligation is satisfied (i.e. when the control of an instrument has passed to the customer; typically, at shipping point). When the instrument is placed under a reagent rental agreement, the Company’s customers generally agree to fixed term agreements, which can be extended, and incremental charges on each consumable diagnostic test purchased. Revenue from the sale of consumable diagnostic tests (under a reagent rental agreement) is recognized upon shipment. The transaction price from consumables purchases is allocated between the lease of the instrument (under a contingent rent methodology as provided for in ASC 840, Leases), and the consumables when related performance obligations are satisfied as a component of lease and product revenue. Revenue associated with reagent rental consumable purchases is currently classified as variable consideration and constrained until a purchase order is received and related performance obligations have been satisfied. Shipping and handling costs billed to customers in connection with a product sale are recorded as a component of the transaction price and allocated to product revenue in the consolidated statements of operations and comprehensive loss as they are incurred by the Company in fulfilling its performance obligations.

Direct sales of instruments include warranty, maintenance and technical support services typically for one year following the installation of the purchased instrument (“Maintenance Services”). Warranty and Maintenance Services are separate performance obligations as they are service based warranties and are recognized straight-line over the service delivery period. After the completion of the initial Maintenance Services period, customers have the option to renew or extend the Maintenance Services typically for additional one-year periods in exchange for additional consideration. The extended Maintenance Services are also service based warranties that represent separate purchasing decisions. The Company recognizes revenue allocated to the extended Maintenance Services performance obligation straight-line over the service delivery period.

The Company warrants that consumable diagnostic tests will be free from defects, when handled according to product specifications, for the stated life of the product. To fulfill valid warranty claims, the Company provides replacement product free of charge. Accordingly, the Company accrues warranty expense associated with the estimated defect rates of the consumable diagnostic tests.

Revenue earned from activities performed pursuant to research and development agreements is reported as research revenue in the consolidated statements of operations and comprehensive loss, and is recognized overtime using an input method as the work is completed, limited to payments earned. The related costs are expensed as incurred as research and development expense. The timing of receipt of cash from the Company’s research and development agreements generally differs from when revenue is recognized. Milestones are contingent on the occurrence of future events and are considered variable consideration being constrained until the Company believes a significant revenue reversal will not occur. Refer to Footnote 11 for further details regarding the Company’s research and development arrangements.

Disaggregation of Revenue

We disaggregate our revenue from contracts with customers by type of products and services, as we believe it best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The following table disaggregates our revenue by major source (in thousands):

	Three months ended, March 31, 2018
Product Revenue
Instruments	$	221
Consumables		746
Instrument Rentals		81
Total Product Revenue		1,048
Research Revenue		1,263
Total Revenue	$	2,311

Remaining Performance Obligations

Remaining performance obligations represent the transaction price of firm orders for which work has not been performed or goods and services have not been delivered. As of March 31, 2018, the aggregate amount of transaction price allocated to remaining performance obligations for contracts with an original duration greater than one year was $2.3 million. We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed. The Company expects to recognize revenue on approximately 98% of the remaining performance obligations over the next nine months with the remainder recognized thereafter.

Significant Judgments

Our contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. Once we determine the performance obligations, the Company determines the transaction price, which includes estimating the amount of variable consideration to be included in the transaction price, if any. We then allocate the transaction price to each performance obligation in the contract based on a relative stand-alone selling price method. The corresponding revenue is recognized as the related performance obligations are satisfied as discussed in the revenue categories above.

Judgment is required to determine the standalone selling price for each distinct performance obligation. We determine standalone selling price based on the price at which the performance obligation is sold separately. If the standalone selling price is not observable through past transactions, we estimate the standalone selling price taking into account available information such as market conditions and the expected costs and margin related to the performance obligations.

Contract Liabilities

The Company’s contract liabilities consist of upfront payments for research and development contracts and Maintenance Services on instrument sales. We classify these contract liabilities in deferred revenue as current or noncurrent based on the timing of when we expect to recognize revenue. Revenue recognized, in the first quarter of 2018, relating to contract liabilities at December 31, 2017 was $1.3 million and related to performance of research and development services and straight-line revenue recognition associated with maintenance agreements.

Cost to Obtain and Fulfill a Contract

The Company does not meet the recoverability criteria to capitalize costs to obtain or fulfill instrument purchases. Reagent rental agreements do not meet the recoverability criteria to capitalize costs to obtain the contracts and the costs to fulfill the contracts are under the scope of ASC 840. At the end of each reporting period, the Company assesses whether any circumstances have changed to meet the criteria for capitalization. The Company did not incur any expenses to obtain research and development agreements and costs to fulfill those contracts do not generate or enhance resources of the entity. As such, no costs to obtain or fulfill a contract have been capitalized at period end.

Cost of Product Revenue

Cost of product revenue includes the cost of materials, direct labor and manufacturing overhead costs used in the manufacture of consumable diagnostic tests sold to customers and related license and royalty fees. Cost of product revenue also includes depreciation on revenue generating T2Dx instruments that have been placed with customers under reagent rental agreements; costs of materials, direct labor and manufacturing overhead costs on the T2Dx instruments sold to customers; and other costs such as customer support costs, royalties and license fees, warranty and repair and maintenance expense on the T2Dx instruments that have been placed with customers under reagent rental agreements.

Research and Development Costs

Costs incurred in the research and development of the Company’s product candidates are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including activities associated with performing services under research revenue arrangements, costs associated with the manufacture of developed products and include salaries and benefits, stock compensation, research‑related facility and overhead costs, laboratory supplies, equipment and contract services.

Recent Accounting Standards

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

Accounting Standards Adopted

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASC 2016-15”), which provides guidance on the classification of certain specific cash flow issues including debt prepayment or extinguishment costs, settlement of certain debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of certain insurance claims and distributions received from equity method investees. The standard requires the use of a retrospective approach to all periods presented, but may be applied prospectively if retrospective application would be impracticable. The guidance is effective for public entities for fiscal years beginning after December 15, 2017, and interim periods within those years, and early application is permitted. The Company has adopted ASU 2016-15 retrospectively and has reflected the statement of cash flows in accordance with this guidance.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASU 2016-18”), which requires that a statement of cash flows explains the change in the total of cash, cash equivalents and restricted cash during the period. Amounts described as restricted cash should be included with cash and cash equivalents when reconciling the beginning of period and end of period amounts shown on the statement of cash flows. The Company has reflected restricted cash with cash and cash equivalents when reconciling the beginning and end of period amounts shown on the statement of cash flows in accordance with ASU 2016-18.

In June 2014, the FASB issued amended guidance, ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which is applicable to revenue recognition that will now be effective for the Company for the year ending December 31, 2018, as a result of the deferral of the effective date adopted by the FASB in July 2015. The new guidance must be adopted using either a full retrospective approach for all periods presented or a modified retrospective approach. Early adoption prior to the original adoption date of ASU 2014-09 is not permitted. The new guidance applies a more principles-based approach to revenue recognition. The Company adopted ASU 2014-09 on January 1, 2018 using the modified retrospective method for all contracts not completed as of the date of adoption. For contracts that were modified before the effective date, the Company reflected the aggregate effect of all modifications when identifying performance obligations and allocating transaction price, which did not have a material effect on the adjustment to accumulated deficit. The reported results for 2018 reflect the application of ASU 2014-09 guidance while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition.

Accounting Standards Issued, Not Adopted

In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”), which applies to all leases. Under ASU 2016-02, a right-of-use asset and lease obligation will be recorded for all leases, whether operating or financing leases, while the statement of operations will reflect lease expense for operating leases and amortization and interest expense for financing leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those years, which is the year ended December 31, 2019 for the Company. Entities are required to use a modified retrospective approach of adoption for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. Full retrospective application is prohibited. The Company is evaluating the new guidance and the expected effect on the Company’s consolidated financial statements.

Emerging Growth Company Status

In April 2012, the Jumpstart Our Business Startups Act, or the JOBS Act, was enacted in the United States. Section 107 of the JOBS Act provides that an “emerging growth company” can take advantage of the extended transition period provided in Section 7(a)(2)(B) of the Securities Act, as amended, for complying with new or revised accounting standards. Thus, an emerging growth company can delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have irrevocably elected not to avail ourselves of this extended transition period and, as a result, we will adopt new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth companies.

Fair Value Measurements

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

The Company measures the following financial assets at fair value on a recurring basis. There were no transfers between levels of the fair value hierarchy during any of the periods presented. The following tables set forth the Company’s financial assets carried at fair value categorized using the lowest level of input applicable to each financial instrument as of March 31, 2018 and December 31, 2017 (in thousands):

	Balance at March 31, 2018		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash	$	6,319	$	6,319	$	—	$	—
Money market funds		23,414		23,414		—		—
Restricted cash		180		180		—		—
	$	29,913	$	29,913	$	—	$	—


Liabilities:
Derivative liability	$	2,096	$	—	$	—	$	2,096
	$	2,096	$	—	$	—	$	2,096

	Balance at December 31, 2017		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash	$	3,463	$	3,463	$	—	$	—
Money market funds		38,336		38,336		—		—
Restricted cash		260		260		—		—
	$	42,059	$	42,059	$	—	$	—


Liabilities:
Derivative liability	$	2,238	$	—	$	—	$	2,238
	$	2,238	$	—	$	—	$	2,238

The Company’s Term Loan Agreement with CRG (Note 6) contains certain provisions that change the underlying cash flows of the instrument, including an interest-only period dependent on the achievement of receiving 510(k) clearance for the marketing of T2Bacteria by the FDA on or before April 30, 2018 (the “Approval Milestone”), and acceleration of the obligations under the Loan Agreement under an event of default. In addition, under certain circumstances, a default interest rate of an additional 4.0% per annum will apply at the election of CRG on all outstanding obligations during the occurrence and continuance of an event of default. The Company concluded that these features are not clearly and closely related to the host instrument, and represent a single compound derivative and is required to be re-measured at fair value on a quarterly basis.

During the fourth quarter of 2017, the Company received communication from the FDA that suggested the approval timeline of T2Bacteria could be longer than the Company initially anticipated. The delay resulted in an increase in the probability of not achieving the Approval Milestone by April 30, 2018, as well an increase in the probability of the payment of contingent interest in future periods, based on the contractual payments that exist as of December 31, 2017. At December 31, 2017, the Company recorded a derivative liability related to the Company’s debt agreement with CRG of $2.2 million. The estimated fair value of the derivative liability was determined using a probability-weighted discounted cash flow model that includes principal and interest payments under the following scenarios: FDA approval by April 30, 2018 (40%), FDA approval after April 30, 2018 (20%) and no FDA approval (40%).

In March 2018, the Term Loan Agreement was amended to extend the Approval Milestone to June 30, 2018, the additional $10.0 million funding through September 27, 2018 and reduce the fiscal year 2018 revenue target to $7.0 million. The fair value of the derivative at March 31, 2018 is $2.1 million. The estimated fair value of the derivative liability was determined using a probability-weighted discounted cash flow model that includes principal and interest payments under the following scenarios: FDA approval by June 30, 2018 (55%), FDA approval after June 30, 2018 (5%) and no FDA approval (40%). Should the Company’s assessment of these probabilities change, including amendments of certain revenue targets, there could be a change to the fair value of the derivative liability.

The following table provides a roll-forward of the fair value of the derivative liability (in thousands):

Balance at December 31, 2017	$	2,238
Change in fair value of derivative liability, recorded as interest expense		(142	)
Balance at March 31, 2018	$	2,096

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Restricted Cash	3 Months Ended
Restricted Cash	Mar. 31, 2018
Restricted Cash [Abstract]
Restricted Cash	4. Restricted Cash The Company is required to maintain a security deposit for its operating lease agreement for the duration of the lease agreement and for its credit cards as long as they are in place. At March 31, 2018 and December 31, 2017, the Company had certificates of deposit for $180,000 and $260,000, respectively, which represented collateral as security deposits for its operating lease agreement for its facility and its credit cards. The $80,000 change is classified as unrestricted cash at March 31, 2018.

Supplemental Balance Sheet Information

3 Months Ended

Mar. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Supplemental Balance Sheet Information

5. Supplemental Balance Sheet Information

Inventories

Inventories are stated at the lower of cost or net realizable value on a first-in, first-out basis and are comprised of the following (in thousands):

	March 31, 2018		December 31, 2017
Raw materials	$	635	$	539
Work-in-process		1,066		562
Finished goods		381		243
Total inventories, net	$	2,082	$	1,344

Property and Equipment

Property and equipment consists of the following (in thousands):

	March 31, 2018			December 31, 2017
Office and computer equipment	$	409		$	409
Software		743			743
Laboratory equipment		4,319			4,224
Furniture		200			200
Manufacturing equipment		910			910
Manufacturing tooling and molds		255			255
T2-owned instruments and components		6,638			7,370
Leasehold improvements		3,437			3,437
Construction in progress		1,551			1,591
		18,462			19,139
Less accumulated depreciation and amortization		(9,752	)		(9,124	)
Property and equipment, net	$	8,710		$	10,015

Construction in progress is primarily comprised of equipment and leasehold improvement projects that have not been placed in service. T2-owned instruments and components is comprised of raw materials and work-in-process inventory that are expected to be used or used to produce T2-owned instruments, based on our business model and forecast, and completed instruments that will be used for internal research and development, clinical studies or reagent rental agreements with customers. At March 31, 2018, there were no raw materials and work-in-process inventory in T2-owned instruments and components compared to $0.8 million at December 31, 2017. Completed T2-owned instruments are placed in service once installation procedures are completed and are depreciated over five years. Depreciation expense for T2-owned instruments placed at customer sites pursuant to reagent rental agreements is recorded as a component of cost of product revenue and totaled approximately $0.2 million for the three months ended March 31, 2018 and 2017. Depreciation expense for T2-owned instruments used for internal research and development and clinical studies is recorded as a component of research and development expense. During the fourth quarter of 2017, the Company received communication from the FDA that suggested the approval timeline would be longer than the Company initially anticipated. The Company assessed the recoverability of T2-owned instruments based on delayed T2Bacteria cash flows and recorded an impairment charge of $2.6 million, related to T2-owned instruments and components, which was recorded in the cost of product revenue as of December 31, 2017. The fair value used in the impairment calculation was based on the best estimated selling price of the underlying T2-owned instruments, less the estimated cost to sell the instruments. The Company did not record any impairment charges in the three months ended March 31, 2018.

Accrued Expenses

Accrued expenses consist of the following (in thousands):

	March 31, 2018		December 31, 2017
Accrued payroll and compensation	$	2,899	$	2,793
Accrued research and development expenses		453		818
Accrued professional services		698		1,018
Other accrued expenses		1,556		1,589
Total accrued expenses	$	5,606	$	6,218

At March 31, 2018 and December 31, 2017, a fee associated with the Company’s Term Loan Agreement (Note 6) of $0.8 million and $0.6 million, respectively, is included in accrued expenses and other current liabilities, to match the classification of the associated debt.

Notes Payable

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

Notes Payable

6. Notes Payable

Future principal payments on the notes payable are as follows (in thousands):

	March 31, 2018			December 31, 2017
Term loan agreement, net of deferred issuance costs of $2.5 million and $3.0 million, respectively	$	39,782		$	39,228
Equipment lease credit facility, net of deferred issuance cost of $29 thousand and $45 thousand, respectively		2,130			2,476
Total notes payable		41,912			41,704
Less: current portion of notes payable		(41,303	)		(40,696	)
Notes payable, net of current portion	$	609		$	1,008

The Term Loan Agreement with CRG is classified as a current liability on the balance sheet at March 31, 2018 and December 31, 2017, based on the Company’s consideration of the probability of violating a minimum liquidity covenant included in the Term Loan Agreement. The contractual terms of the agreement require payments of $5.8 million, $23.0 million and $17.2 million during the years ended December 31, 2020, 2021 and 2022, respectively.

Term Loan Agreement

In December 2016, the Company entered into a Term Loan Agreement (the “Term Loan Agreement”) with CRG. The Company initially borrowed $40.0 million pursuant to the Term Loan Agreement and may borrow up to an additional $10.0 million at any time through and including July 27, 2018, provided that, among other conditions, the Company receives 510(k) clearance for the marketing of T2Bacteria by the FDA on or before April 30, 2018. The Term Loan Agreement has a six-year term with three years (through December 30, 2019) of interest-only payments, which period shall be extended to four years (through December 30, 2020) if the Company achieves the Approval Milestone, after which quarterly principal and interest payments will be due through the December 30, 2022 maturity date. Interest on the amounts borrowed under the Term Loan Agreement accrues at an annual fixed rate of (a) prior to the Approval Milestone, 12.5%, 4.0% of which may be deferred during the interest-only period by adding such amount to the aggregate principal loan amount and (b) following the Approval Milestone, 11.5%, 3.5% of which may be deferred during the interest-only period by adding such amount to the aggregate principal loan amount. In addition, if the Company achieves certain financial performance metrics, the loan will convert to interest-only until the December 30, 2022 maturity, at which time all unpaid principal and accrued unpaid interest will be due and payable. The Company is required to pay CRG a financing fee based on the loan principal amount drawn. The Company is also required to pay a final payment fee of 8.0% of the principal outstanding upon repayment.

The Company may prepay all or a portion of the outstanding principal and accrued unpaid interest under the Term Loan Agreement at any time upon prior notice subject to a certain prepayment fee during the first five years of the term and no prepayment fee thereafter. As security for its obligations under the Term Loan Agreement the Company entered into a security agreement with CRG whereby the Company granted a lien on substantially all of its assets, including intellectual property. The Term Loan Agreement also contains customary affirmative and negative covenants for a credit facility of this size and type, including a requirement to maintain a minimum cash balance. The Term Loan Agreement also requires the Company to achieve certain revenue targets, whereby the Company is required to pay double the amount of any shortfall as an acceleration of principal payments. The revenue target for fiscal 2018 is $7.0 million. The Term Loan Agreement includes a subjective acceleration clause whereby an event of default, including a material adverse change in the business, operations, or conditions (financial or otherwise), could result in the acceleration of the obligations under the Term Loan Agreement. Under certain circumstances, a default interest rate of an additional 4.0% per annum will apply at the election of CRG on all outstanding obligations during the occurrence and continuance of an event of default. CRG has not exercised its right under this clause, as there have been no such events.

During the fourth quarter of 2017, the Company received communication from the FDA that suggested the approval timeline of T2Bacteria would be longer than the Company initially anticipated. The delay resulted in an increase in the probability of not achieving the Approval Milestone by April 30, 2018, as well an increase in the probability of the payment of contingent interest in future periods, based on the contractual payments requirements that exist as of December 31, 2017.

In March 2018, the Term Loan Agreement was amended to extend the Approval Milestone to June 30, 2018, extend the additional $10.0 million funding through September 27, 2018 and reduce the fiscal year 2018 revenue target to $7.0 million. The Company assessed the terms and features of the Term Loan Agreement, including the interest-only period dependent on the achievement of the Approval Milestone by June 30, 2018, and acceleration of the obligations under the Term Loan Agreement under an event of default, of the Term Loan Agreement in order to identify any potential embedded features that would require bifurcation. In addition, under certain circumstances, a default interest rate of an additional 4.0% per annum will apply at the election of CRG on all outstanding obligations during the occurrence and continuance of an event of default, The Company concluded that the features of the Term Loan Agreement are not clearly and closely related to the host instrument, and represent a single compound derivative and is required to be re-measured at fair value on a quarterly basis. At December 31, 2017, the Company recorded a derivative liability related to the Company’s debt agreement with CRG of $2.2 million. The fair value of the derivative at March 31, 2018 is $2.1 million.

In December 2016, pursuant to the Term Loan Agreement, the Company made an initial draw of $39.2 million, net of financing fees. The Company used approximately $28.0 million of the initial proceeds to repay approximately $27.5 million of outstanding debt pursuant to the Loan and Security Agreement and to repay approximately $0.5 million of outstanding debt pursuant to the Promissory Note. Upon the repayment of all amounts owed by the Company under these agreements, all commitments were terminated and all security interests granted by the Company were released.

In connection with the Term Loan Agreement entered into in December 2016, the Company issued to CRG four separate warrants to purchase a total of 528,958 shares of the Company’s common stock. The warrants are exercisable any time prior to December 30, 2026 at a price of $8.06 per share, with typical provisions for termination upon a change of control or a sale of all or substantially all of the assets of the Company. The warrants are classified within shareholders’ equity, and the proceeds were allocated between the debt and warrants based on their relative fair value. The fair value of the warrants was determined by the Black Scholes Merton option pricing model. The fair value of the warrants at issuance on December 30, 2016 was $1.8 million.

Equipment Lease Credit Facility

In October 2015, the Company signed a $10.0 million Credit Facility (the “Credit Facility”) with Essex Capital Corporation (the “Lessor”) to fund capital equipment needs. As one of the conditions of the Term Loan Agreement, the Credit Facility is capped at a maximum of $5.0 million. Under the Credit Facility, Essex will fund capital equipment purchases presented by the Company. The Company will repay the amounts borrowed in 36 equal monthly installments from the date of the amount funded. At the end of the 36 month lease term, the Company has the option to (a) repurchase the leased equipment at the lesser of fair market value or 10% of the original equipment value, (b) extend the applicable lease for a specified period of time, which will not be less than one year, or (c) return the leased equipment to the Lessor.

In April 2016 and June 2016, the Company completed the first two draws under the Credit Facility, of $2.1 million and $2.5 million, respectively. The Company will make monthly payments of $67,000 under the first draw and $79,000 under the second draw. The borrowings under the Credit Facility are treated as capital leases. The amortization of the assets conveyed under the Credit Facility is included as a component of depreciation expense.

Stockholders' Equity	3 Months Ended
Stockholders' Equity	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity Private Investment in Public Equity Financing On September 21, 2016, Canon U.S.A., Inc. (“Canon”) became a related party when the Company sold 6,055,341 shares of its common stock (the “Canon Shares”) to Canon at $6.56 per share, the closing price on this date, for an aggregate cash purchase price of $39.7 million. As of September 21, 2016, the Canon Shares represented 19.9% of the outstanding shares of common stock of the Company. In connection with the sale of the Canon Shares, the Company agreed to grant Canon certain board designation rights, including the right to initially appoint a Class I director to the Company’s board of directors. On March 20, 2017, the Company filed with the Securities and Exchange Commission (the “SEC”) a registration statement on Form S-3 for purposes of registering the resale of the Canon Shares with the SEC. Confidentially Marketed Public Offering On September 15, 2017, the Company sold 5,031,250 shares of its common stock in a CMPO at $4.00 per share, for an aggregate gross cash purchase price of $20.1 million, or proceeds of $18.8 million after underwriters discount and expenses. Common Stock The Company authorized 200,000,000 shares of common stock, $0.001 par value per share, of which 36,019,883 and 35,948,900 were outstanding as of March 31, 2018 and December 31, 2017, respectively.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

Stock Incentive Plans

2006 Stock Incentive Plan

The Company’s 2006 Employee, Director and Consultant Stock Option Plan (“2006 Plan”) was established for granting stock incentive awards to directors, officers, employees and consultants of the Company. Upon closing of the Company’s IPO in August 2014, the Company ceased granting stock incentive awards under the 2006 Plan. The 2006 Plan provided for the grant of incentive and non-qualified stock options and restricted stock grants as determined by the Company’s board of directors. Under the 2006 Plan, stock options were generally granted with exercise prices equal to or greater than the fair value of the common stock as determined by the board of directors, expired no later than 10 years from the date of grant, and vest over various periods not exceeding 4 years.

2014 Stock Incentive Plan

The Company’s 2014 Incentive Award Plan (“2014 Plan”, and together with the 2006 Plan, the “Stock Incentive Plans”), provides for the issuance of shares of common stock in the form of stock options, awards of restricted stock, awards of restricted stock units, performance awards, dividend equivalent awards, stock payment awards and stock appreciation rights to directors, officers, employees and consultants of the Company. Since the establishment of the 2014 Plan, the Company has only granted stock options and restricted stock units. Generally, stock options are granted with exercise prices equal to or greater than the fair value of the common stock on the date of grant, expire no later than 10 years from the date of grant, and vest over various periods not exceeding 4 years.

The number of shares reserved for future issuance under the 2014 Plan is the sum of (1) 823,529 shares, (2) any shares that were granted under the 2006 Plan which are forfeited, lapsed unexercised or are settled in cash subsequent to the effective date of the 2014 Plan and (3) an annual increase on the first day of each calendar year beginning January 1, 2015 and ending on January 1, 2024, equal to the lesser of (A) 4% of the shares outstanding (on an as-converted basis) on the final day of the immediately preceding calendar year, and (B) such smaller number of shares determined by the Company’s Board of Directors. As of March 31, 2018, there were 513,627 shares available for future grant under the 2014 Plan.

Inducement Award Plan

The Company’s Inducement Award Plan (“Inducement Plan”), which was adopted in March 2018, provides for the granting of equity awards to new employees, which includes options, restricted stock awards, restricted stock units, performance awards, dividend equivalent awards, stock payment awards and stock appreciation rights. The aggregate number of shares of common stock which may be issued or transferred pursuant to awards under the Inducement Plan is 625,000 shares. Any awards that forfeit, expire, lapse, or are settled for cash without the delivery of shares to the holder are available for the grant of an award under the Inducement Plan. Any shares repurchased by or surrendered to the Company that are returned shall be available for grant of an award under the Inducement Plan. The payment of dividend equivalents in cash in conjunction with any outstanding Award shall not be counted against the shares available for issuance under the Inducement Plan. As of March 31, 2018, there were 400,000 shares available for future grant under the Inducement Plan.

Stock Options

During the three months ended March 31, 2018 and 2017, the Company granted stock options with an aggregate fair value of $4.4 million and $1.7 million, respectively, which are being amortized into compensation expense over the vesting period of the stock options as the services are being provided.

The following is a summary of stock option activity under the Plans (in thousands, except share and per share amounts):

	Number of Shares			Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (In years)		Aggregate Intrinsic Value
Outstanding at December 31,2017		3,785,083		$	7.31		6.88	$	1,989
Granted		1,303,750			5.47
Exercised		(21,014	)		3.21				51
Forfeited		(503,693	)		6.56
Cancelled		(22,044	)		14.07
Outstanding at March 31, 2018		4,542,082			6.85		7.10		6,824
Exercisable at March 31, 2018		2,431,162			7.30		5.12		4,816
Vested or expected to vest at March 31, 2018		4,046,752			6.98		6.79		6,315

Included in the stock options outstanding as of December 31, 2017 are 106,066 performance based options, which were forfeited during the period ended March 31, 2018 as the performance conditions were not achieved.

The weighted-average grant date fair values of stock options granted in the three month periods ended March 31, 2018 and 2017 were $3.41 per share and $3.34 per share, respectively, and were calculated using the following estimated assumptions:

	Three Months Ended
	March 31,
	2018			2017
Weighted-average risk-free interest rate		2.63	%		2.02	%
Expected dividend yield		—	%		—	%
Expected volatility		68	%		63	%
Expected terms	6.0 years			6.0 years

The total fair values of stock options that vested during the three months ended March 31, 2018 and 2017 were $0.8 million and $1.1 million, respectively.

As of March 31, 2018, there was $7.8 million of total unrecognized compensation cost related to unvested stock options granted under the Stock Incentive Plans. Total unrecognized compensation cost will be adjusted for future changes in the estimated forfeiture rate. The Company expects to recognize that cost over a remaining weighted-average period of 3.07 years as of March 31, 2018.

Restricted Stock Units

During the three months ended March 31, 2018, the Company awarded shares of restricted stock units to certain employees and directors at no cost to them, which cannot be sold, assigned, transferred or pledged during the restriction period. The restricted stock and restricted stock units, excluding any restricted stock units with market conditions, vest through the passage of time, assuming continued employment. Restricted stock units are not included in issued and outstanding common stock until the shares are vested and released. The fair value of the award at the time of the grant is expensed on a straight line basis. The granted restricted stock units had an aggregate fair value of $6.2 million, which are being amortized into compensation expense over the vesting period of the options as the services are being provided.

Included in the restricted stock units granted during the three months ended March 31, 2018 are 1,179,089 restricted stock units with market conditions, which vest upon the achievement of stock price targets. The compensation cost for restricted stock units with market conditions is being recorded over the derived service period and was $0.2 million for the three months ended March 31, 2018.

The following is a summary of restricted stock unit activity under the 2014 Plan (in thousands, except share and per share amounts):

	Number of Shares			Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2017		606,497			5.23
Granted		1,217,189			5.06
Vested		(64,772	)		5.82
Forfeited		(44,451	)		5.72
Cancelled		—			—
Nonvested at March 31, 2018		1,714,463			5.08

During the three months ended March 31, 2018, 64,772 restricted stock units vested and 14,803 shares were withheld to cover employee tax. As of March 31, 2018, there was $7.7 million of total unrecognized compensation cost related to unvested restricted stock units granted under the Stock Incentive Plans, including the unrecognized compensation expense of stock options with market conditions deemed probable of vesting. The Company expects to recognize that cost over a remaining weighted-average period of 1.02 years, as of March 31, 2018.

Stock-Based Compensation Expense

The following table summarizes the stock-based compensation expense resulting from awards granted under stock incentive plans, including the 2014 ESPP, that was recorded in the Company’s results of operations for the periods presented (in thousands):

	Three Months Ended March 31,
	2018		2017
Cost of product revenue	$	22	$	30
Research and development		369		302
Selling, general and administrative		966		796
Total stock-based compensation expense	$	1,357	$	1,128

For the three months ended March 31, 2018 and 2017, $24,000 and $29,000 of stock-based compensation expenses were capitalized as part of inventory or T2Dx instruments and components, respectively.

Warrants	3 Months Ended
Warrants	Mar. 31, 2018
Text Block [Abstract]
Warrants	9. Warrants In connection with the Term Loan Agreement entered into in December 2016, the Company issued to CRG four separate warrants to purchase a total of 528,958 shares of the Company’s common stock. The warrants are exercisable any time prior to December 30, 2026 at a price of $8.06 per share, with typical provisions for termination upon a change of control or a sale of all or substantially all of the assets of the Company. The warrants are classified within shareholders’ equity, and the proceeds were allocated between the debt and warrants based on their relative fair value. The fair value of the warrants was determined by the Black-Scholes-Merton option pricing model. The fair value of the warrants at issuance was $1.8 million.

Net Loss Per Share

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Net Loss Per Share

10. Net Loss Per Share

The following shares were excluded from the calculation of diluted net loss per share applicable to common stockholders, prior to the application of the treasury stock method, because their effect would have been anti-dilutive for the periods presented:

	Three Months Ended March 31,
	2018		2017
Options to purchase common shares		4,542,082		4,152,265
Restricted stock units		1,714,463		520,120
Warrants to purchase common stock		528,958		528,958
Total		6,785,503		5,201,343

Co-Development Agreements	3 Months Ended
Co-Development Agreements	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Co-Development Agreements	11. Co-Development Agreements Canon US Life Sciences On September 21, 2016, Canon became a related party when the Company sold the Canon Shares for an aggregate cash purchase price of $39.7 million, which represented 19.9% of the outstanding shares of common stock of the Company. On February 3, 2015, the Company entered into a Co-Development Partnership Agreement (the “Co-Development Agreement”) with Canon U.S. Life Sciences, Inc. (“Canon US Life Sciences”) to develop a diagnostic test panel to rapidly detect Lyme disease. Under the terms of the Co-Development Agreement, the Company received an upfront payment of $2.0 million from Canon US Life Sciences, and the agreement includes an additional $6.5 million of consideration upon achieving certain development and regulatory milestones for total aggregate payments of up to $8.5 million. In October 2015, the Company achieved a specified technical requirement and received $1.5 million related to the achievement of the milestone. The Company is eligible to receive an additional $5.0 million under the arrangement, in two milestone payments of $2.0 million and $3.0 million, related to the achievement of additional development and regulatory milestones. All payments under the Co-Development Agreement are non-refundable once received. The Company will retain exclusive worldwide commercialization rights of any products developed under the Co-Development Agreement, including sales, marketing and distribution and Canon US Life Sciences will not receive any commercial rights and will be entitled to only receive royalty payments on the sales of all products developed under the Co-Development Agreement. Either party may terminate the Co-Development Agreement upon the occurrence of a material breach by the other party (subject to a cure period). The Company evaluated the promised goods and services under the Co-Development Agreement and determined that the Co-Development Agreement included one performance obligation, the research and development services. The Company is recognizing revenue for research and development services as a component of research revenue in the condensed consolidated financial statements over time, as the services are delivered. The Company uses the input method by allocating and recognizing revenue over time based on the total full-time equivalent effort incurred to date as a percentage of total full-time equivalent time expected, limited to payments earned. Costs incurred to deliver the services under the Co-Development Agreement are recorded as research and development expense in the condensed consolidated financial statements. The Company did not record any revenue for the three months ended March 31, 2018 and recorded revenue of $0.3 million during the three months ended March 31, 2017, under the Co-Development Agreement, and expects to record revenue over the next two years, provided development milestones are achieved. Allergan Sales, LLC On November 1, 2016, the Company entered into a Co-Development, Collaboration and Co-Marketing Agreement (the “Allergan Agreement”) with Allergan Sales, LLC (“Allergan Sales”) to develop (1) a direct detection diagnostic test panel that adds one additional bacteria species to the existing T2Bacteria product candidate (the “T2Bacteria II Panel”), and (2) a direct detection diagnostic test panel for testing drug resistance directly in whole blood (the “T2GNR Panel” and, together with the T2Bacteria II Panel, the “Developed Products”). In addition, both the Company and Allergan Sales will participate in a joint research and development committee and Allergan Sales will receive the right to cooperatively market the T2Candida, T2Bacteria, and the Developed Products under the Allergan Agreement to certain agreed-upon customers. Under the terms of the Allergan Agreement, the Company received an upfront payment of $2.0 million from Allergan Sales and will receive additional milestone payments upon achieving certain developmental milestones for total aggregate payments of up to $4.0 million. All payments under the Allergan Agreement are non-refundable once received. The Company will retain exclusive worldwide commercialization rights of any products developed under the Allergan Agreement, including distribution, subject to Allergan Sales’ right to co-market the Developed Products. Allergan Sales, at its election, may co-market T2Candida, T2Bacteria and the Developed Products worldwide to certain agreed-upon customers and will receive a royalty based on its sales for a period of time. The Company evaluated the promised goods and services under the Allergan Agreement and determined that the Allergan Agreement included two performance obligations, the research and development services for the T2Bacteria II Panel and the research and development services for the T2GNR Panel. The Company uses the input method by allocating and recognizing revenue over time based on the total full-time equivalent effort incurred to date as a percentage of total full-time equivalent time expected, limited to payments earned. Costs incurred to deliver the services under the Allergan Agreement are recorded as research and development expense in the consolidated financial statements. The Company recorded revenue of $1.3 million and $38,000 for the three months ended March 31, 2018 and 2017, respectively, under the Allergan Agreement and expects to record revenue over the next nine months, provided development and regulatory milestones are achieved. CARB-X In March 2018, the Company was awarded a grant of up to $2.0 million from CARB-X. The collaboration with CARB-X will be used to accelerate the development of new tests to identify bacterial pathogens and resistance markers directly in whole blood more rapidly than is possible using today’s diagnostic tools. The new tests aim to expand the T2Dx instrument product line by detecting 20 additional bacterial species and resistance targets, with a focus on blood borne pathogens on the United States Centers for Disease Control and Prevention (“CDC”) antibiotic resistance threat list. Under this cost-sharing agreement, the Company may be reimbursed up to $1.1 million, with the possibility of up to an additional $0.9 million based on the achievement of certain project milestones.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation

Unaudited Interim Financial Information


Most of the Company’s contracts with customers contain multiple performance obligations. For these contracts, the Company accounts for individual performance obligations separately if they are distinct. The transaction price is allocated to the separate performance obligations on a relative standalone selling price basis.

Disaggregation of Revenue

	Three months ended, March 31, 2018
Product Revenue
Instruments	$	221
Consumables		746
Instrument Rentals		81
Total Product Revenue		1,048
Research Revenue		1,263
Total Revenue	$	2,311

Remaining Performance Obligations

Significant Judgments

Contract Liabilities

Cost to Obtain and Fulfill a Contract

Cost of Product Revenue

Research and Development Costs

Recent Accounting Standards

Accounting Standards Adopted

Accounting Standards Issued, Not Adopted

Emerging Growth Company Status

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Disaggregation of Revenue by Major Source

The following table disaggregates our revenue by major source (in thousands):

	Three months ended, March 31, 2018
Product Revenue
Instruments	$	221
Consumables		746
Instrument Rentals		81
Total Product Revenue		1,048
Research Revenue		1,263
Total Revenue	$	2,311

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities at Fair value on a Recurring Basis

	Balance at March 31, 2018		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash	$	6,319	$	6,319	$	—	$	—
Money market funds		23,414		23,414		—		—
Restricted cash		180		180		—		—
	$	29,913	$	29,913	$	—	$	—


Liabilities:
Derivative liability	$	2,096	$	—	$	—	$	2,096
	$	2,096	$	—	$	—	$	2,096

	Balance at December 31, 2017		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash	$	3,463	$	3,463	$	—	$	—
Money market funds		38,336		38,336		—		—
Restricted cash		260		260		—		—
	$	42,059	$	42,059	$	—	$	—


Liabilities:
Derivative liability	$	2,238	$	—	$	—	$	2,238
	$	2,238	$	—	$	—	$	2,238

Roll-Forward of Fair Value of Derivative Liability

The following table provides a roll-forward of the fair value of the derivative liability (in thousands):

Balance at December 31, 2017	$	2,238
Change in fair value of derivative liability, recorded as interest expense		(142	)
Balance at March 31, 2018	$	2,096

Supplemental Balance Sheet Information (Tables)

3 Months Ended

Mar. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Inventory

Inventories are stated at the lower of cost or net realizable value on a first-in, first-out basis and are comprised of the following (in thousands):

	March 31, 2018		December 31, 2017
Raw materials	$	635	$	539
Work-in-process		1,066		562
Finished goods		381		243
Total inventories, net	$	2,082	$	1,344

Schedule of Property and Equipment

Property and equipment consists of the following (in thousands):

	March 31, 2018			December 31, 2017
Office and computer equipment	$	409		$	409
Software		743			743
Laboratory equipment		4,319			4,224
Furniture		200			200
Manufacturing equipment		910			910
Manufacturing tooling and molds		255			255
T2-owned instruments and components		6,638			7,370
Leasehold improvements		3,437			3,437
Construction in progress		1,551			1,591
		18,462			19,139
Less accumulated depreciation and amortization		(9,752	)		(9,124	)
Property and equipment, net	$	8,710		$	10,015

Components of Accrued Expenses

Accrued expenses consist of the following (in thousands):

	March 31, 2018		December 31, 2017
Accrued payroll and compensation	$	2,899	$	2,793
Accrued research and development expenses		453		818
Accrued professional services		698		1,018
Other accrued expenses		1,556		1,589
Total accrued expenses	$	5,606	$	6,218

Notes Payable (Tables)

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

Schedule of Debt

Future principal payments on the notes payable are as follows (in thousands):

	March 31, 2018			December 31, 2017
Term loan agreement, net of deferred issuance costs of $2.5 million and $3.0 million, respectively	$	39,782		$	39,228
Equipment lease credit facility, net of deferred issuance cost of $29 thousand and $45 thousand, respectively		2,130			2,476
Total notes payable		41,912			41,704
Less: current portion of notes payable		(41,303	)		(40,696	)
Notes payable, net of current portion	$	609		$	1,008

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following is a summary of stock option activity under the Plans (in thousands, except share and per share amounts):

	Number of Shares			Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (In years)		Aggregate Intrinsic Value
Outstanding at December 31,2017		3,785,083		$	7.31		6.88	$	1,989
Granted		1,303,750			5.47
Exercised		(21,014	)		3.21				51
Forfeited		(503,693	)		6.56
Cancelled		(22,044	)		14.07
Outstanding at March 31, 2018		4,542,082			6.85		7.10		6,824
Exercisable at March 31, 2018		2,431,162			7.30		5.12		4,816
Vested or expected to vest at March 31, 2018		4,046,752			6.98		6.79		6,315

Schedule of Estimated Assumptions Used to Calculate Weighted-Average Grant Date Fair Value of Options Granted

	Three Months Ended
	March 31,
	2018			2017
Weighted-average risk-free interest rate		2.63	%		2.02	%
Expected dividend yield		—	%		—	%
Expected volatility		68	%		63	%
Expected terms	6.0 years			6.0 years

Schedule of Nonvested Restricted Stock Units Activity

The following is a summary of restricted stock unit activity under the 2014 Plan (in thousands, except share and per share amounts):

	Number of Shares			Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2017		606,497			5.23
Granted		1,217,189			5.06
Vested		(64,772	)		5.82
Forfeited		(44,451	)		5.72
Cancelled		—			—
Nonvested at March 31, 2018		1,714,463			5.08

Summary of Stock-Based Compensation Expense for Stock Options Granted that was Recorded in the Company's Results of Operations

	Three Months Ended March 31,
	2018		2017
Cost of product revenue	$	22	$	30
Research and development		369		302
Selling, general and administrative		966		796
Total stock-based compensation expense	$	1,357	$	1,128

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

	Three Months Ended March 31,
	2018		2017
Options to purchase common shares		4,542,082		4,152,265
Restricted stock units		1,714,463		520,120
Warrants to purchase common stock		528,958		528,958
Total		6,785,503		5,201,343

Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash and cash equivalents	$ 29,733	$ 41,799
Accumulated deficit	$ (278,930)	$ (266,117)

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018 USD ($) Segment
Product Information [Line Items]
Number of operating segments \| Segment	1
Aggregate amount of transaction price allocated to remaining performance obligations for contracts with original duration greater than one year	$ 2,300,000
Remaining performance obligation, percentage of revenue expected to be recognized over next nine months	98.00%
Remaining performance obligation, expected timing of satisfaction	The Company expects to recognize revenue on approximately 98% of the remaining performance obligations over the next nine months with the remainder recognized thereafter.
Revenue recognized relating to contract liabilities	$ 1,300,000
Costs to obtain or fulfill contract capitalized	$ 0
Minimum [Member]
Product Information [Line Items]
Aggregate amount of transaction price allocated to remaining performance obligations, original duration	1 year
Maximum [Member]
Product Information [Line Items]
Original expected period of contracts for which value of unsatisfied performance obligations not to be disclosed	1 year
T2 Dx [Member]
Product Information [Line Items]
Maintenance Services period (in years)	1 year
Additional period for Maintenance Service option (in years)	1 year

Summary of Significant Accounting Policies - Disaggregation of Revenue by Major Resource (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,311
Product Instruments [Member]
Disaggregation Of Revenue [Line Items]
Revenue	221
Total Product Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,048
Product Consumables [Member]
Disaggregation Of Revenue [Line Items]
Revenue	746
Research [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,263
Instrument Rentals [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 81

Fair Value Measurements - Schedule of Financial Assets and Liabilities at Fair value on a Recurring Basis (Detail) - Estimate of Fair Value Measurement [Member] - Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Restricted cash	$ 180	$ 260
Total assets	29,913	42,059
Liabilities:
Derivative liability	2,096	2,238
Total Liabilities	2,096	2,238
Cash [Member]
Assets:
Cash	6,319	3,463
Money Market Funds [Member]
Assets:
Cash	23,414	38,336
Level 1 [Member]
Assets:
Restricted cash	180	260
Total assets	29,913	42,059
Level 1 [Member] \| Cash [Member]
Assets:
Cash	6,319	3,463
Level 1 [Member] \| Money Market Funds [Member]
Assets:
Cash	23,414	38,336
Level 3 [Member]
Liabilities:
Derivative liability	2,096	2,238
Total Liabilities	$ 2,096	$ 2,238

Fair Value Measurements - Additional Information (Detail) - CRG [Member] - Term Loan Agreement [Member] - USD ($) $ in Millions	1 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2016	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional interest rate, event of default (as a percent)	4.00%	4.00%	4.00%
Derivative liability	$ 2.1		$ 2.1	$ 2.2
Line of credit, additional borrowing capacity	10.0	$ 10.0	10.0
Debt instrument covenant compliance revenue targeted for fiscal year	$ 7.0		$ 7.0
FDA approval by April 30, 2018 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate				40.00%
FDA approval After April 30, 2018 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate				20.00%
No FDA approval [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate	40.00%			40.00%
FDA approval by June 30, 2018 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate	55.00%
FDA approval After June 30, 2018 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of discount rate	5.00%

Fair Value Measurements - Roll-Forward of Fair Value of Derivative Liability (Detail) - Probability-Weighted Discounted Cash Flow Model [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance at December 31, 2017	$ 2,238
Change in fair value of derivative liability, recorded as interest expense	(142)
Balance at March 31, 2018	$ 2,096

Restricted Cash - Additional Information (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Restricted Cash And Cash Equivalents Items [Line Items]
Unrestricted cash	$ 29,733,000	$ 41,799,000
Certificates of deposit [Member]
Restricted Cash And Cash Equivalents Items [Line Items]
Security deposit	180,000	$ 260,000
Unrestricted cash	$ 80,000

Supplemental Balance Sheet Information - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Raw materials	$ 635	$ 539
Work-in-process	1,066	562
Finished goods	381	243
Total inventories, net	$ 2,082	$ 1,344

Supplemental Balance Sheet Information - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 18,462	$ 19,139
Less accumulated depreciation and amortization	(9,752)	(9,124)
Property and equipment, net	8,710	10,015
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	409	409
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	743	743
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,319	4,224
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	200	200
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	910	910
Manufacturing Tooling and Molds [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	255	255
T2-Owned Instruments and Components [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,638	7,370
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,437	3,437
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,551	$ 1,591

Supplemental Balance Sheet Information - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Supplemental Balance Sheet Information [Line Items]
Impairment charges	$ 0
Raw materials and work-in-process inventory	0	$ 800,000
Transfer from other liabilities to accrued expenses and other current liabilities related to fee from debt	$ 800,000		$ 600,000
T2 Owned Instruments in Service [Member]
Supplemental Balance Sheet Information [Line Items]
Estimated useful lives (in years)	5 years
Depreciation expense recorded as a component of cost of product revenue	$ 200,000	200,000
T2-Owned Instruments and Components [Member]
Supplemental Balance Sheet Information [Line Items]
Impairment charges		$ 2,600,000

Supplemental Balance Sheet Information - Components of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
Accrued payroll and compensation	$ 2,899	$ 2,793
Accrued research and development expenses	453	818
Accrued professional services	698	1,018
Other accrued expenses	1,556	1,589
Total accrued expenses	$ 5,606	$ 6,218

Notes Payable - Schedule of Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument
Total notes payable	$ 41,912	$ 41,704
Less: current portion of notes payable	(41,303)	(40,696)
Notes payable, net of current portion	609	1,008
Medium-term Notes [Member] \| Term Loan Agreement [Member]
Debt Instrument
Total notes payable	39,782	39,228
Line of Credit [Member] \| Equipment Lease Credit Facility [Member]
Debt Instrument
Total notes payable	$ 2,130	$ 2,476

Notes Payable - Schedule of Debt (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Term Loan Agreement [Member] \| Medium-term Notes [Member]
Debt Instrument
Deferred issuance costs	$ 2,500	$ 3,000
Equipment Lease Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument
Deferred issuance costs	$ 29	$ 45

Notes Payable - Term Loan Agreement - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2016 USD ($) Warrant $ / shares shares	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument
Repayments of note payable			$ 352	$ 299
Common Stock [Member]
Debt Instrument
Number of warrants \| Warrant		4
Number of shares issuable for warrants outstanding (in shares) \| shares		528,958
Exercise price of warrants \| $ / shares		$ 8.06
Fair market value of warrants		$ 1,800
Loan and Security Agreement [Member]
Debt Instrument
Repayments of note payable		27,500
Promissory Note [Member]
Debt Instrument
Repayments of note payable		500
CRG [Member] \| Term Loan Agreement [Member]
Debt Instrument
Debt instrument, required payment in December 31, 2020			5,800
Debt instrument, required payment in December 31, 2021			23,000
Debt instrument, required payment in December 31, 2022			17,200
Proceeds from issuance of long-term debt		40,000
Line of credit, additional borrowing capacity	$ 10,000	$ 10,000	10,000
Debt term (in years)		6 years
Debt instrument, term of interest-only payments (in years)		3 years
Debt instrument, extended term interest only payments (in years)		4 years
Final fee as a percentage of the principal outstanding (as a percent)		8.00%
Debt instrument, prepayment fee term (in years)		5 years
Debt instrument covenant compliance revenue targeted for fiscal year	$ 7,000		$ 7,000
Additional interest rate, event of default (as a percent)	4.00%	4.00%	4.00%
Derivative liability	$ 2,100		$ 2,100		$ 2,200
Proceeds from issuance of note payable, net		$ 39,200
Portion of proceeds used for debt repayment		$ 28,000
CRG [Member] \| Term Loan Agreement [Member] \| Prior to Approval Milestone [Member]
Debt Instrument
Annual fixed rate (as a percent)		12.50%
Deferred interest rate (as a percent)		4.00%
CRG [Member] \| Term Loan Agreement [Member] \| Following Approval Milestone [Member]
Debt Instrument
Annual fixed rate (as a percent)		11.50%
Deferred interest rate (as a percent)		3.50%

Notes Payable - Equipment Lease Credit Facility - Additional Information (Detail) - Capital Lease Obligations [Member]	1 Months Ended
	Jun. 30, 2016 USD ($) Draw	Apr. 30, 2016 USD ($)	Oct. 31, 2015 USD ($)
Debt Instrument
Initial borrowing capacity			$ 10,000,000
Maximum borrowings available (up to)			$ 5,000,000
Debt term (in months)			36 months
Repurchase price as percentage of original equipment value that the equipment under lease may be repurchased by lessee			10.00%
Minimum lease period to extend lease (in years)			1 year
Amount of draw	$ 2,500,000	$ 2,100,000
Amount of monthly payment	$ 79,000	$ 67,000
Number of draws \| Draw	2

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Sep. 15, 2017	Sep. 21, 2016	Mar. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Common stock, shares authorized			200,000,000	200,000,000
Common stock, par value (in dollars per share)			$ 0.001	$ 0.001
Common stock, shares outstanding			36,019,883	35,948,900
Private Placement [Member]
Class Of Stock [Line Items]
Number of shares sold		6,055,341
Sale price of stock (in dollars per share)		$ 6.56
Proceeds from private investment in public equity		$ 39.7
Percentage of common shares outstanding (as a percentage)		19.90%
CMPO [Member]
Class Of Stock [Line Items]
Number of shares sold	5,031,250
Sale price of stock (in dollars per share)	$ 4.00
Proceeds from private investment in public equity	$ 20.1
Proceeds from private investment in public equity after underwriters discount and expenses	$ 18.8

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Share-Based Compensation
Fair value of vested stock options	$ 800,000	$ 1,100,000
Unrecognized compensation cost related to unvested stock options	$ 7,800,000
Weighted-average period	3 years 25 days
Stock-based compensation expense	$ 1,357,000	1,128,000
T2Dx Instruments and Components [Member]
Share-Based Compensation
Stock-based compensation expense	$ 24,000	29,000
Performance-based awards [Member]
Share-Based Compensation
Outstanding, end of the period			106,066
Forfeited performance stock based options	106,066
Restricted Stock Units [Member]
Share-Based Compensation
Unrecognized compensation cost related to unvested stock options	$ 7,700,000
Weighted-average period	1 year 7 days
Restricted stock units granted	1,217,189
Restricted stock units, vested	64,772
Shares for withheld to cover employee tax	14,803
2014 Stock Option Plan [Member] \| Stock Options [Member]
Share-Based Compensation
Shares available for future issuance under stock incentive plan	823,529
Percentage of common shares outstanding	4.00%
Shares available for grant	513,627
Inducement Plan [Member]
Share-Based Compensation
Shares available for grant	400,000
Shares available for authorization	625,000
2006 and 2014 Stock Option Plans [Member] \| Stock Options [Member]
Share-Based Compensation
Aggregate fair value of options granted	$ 4,400,000	$ 1,700,000
2006 and 2014 Stock Option Plans [Member] \| Stock Options [Member]
Share-Based Compensation
Outstanding, end of the period	4,542,082		3,785,083
Forfeited performance stock based options	503,693
Weighted average fair value of options granted	$ 3.41	$ 3.34
2006 and 2014 Stock Option Plans [Member] \| Restricted Stock Units [Member]
Share-Based Compensation
Aggregate fair value of options granted	$ 6,200,000
Restricted stock units granted	1,179,089
2006 and 2014 Stock Option Plans [Member] \| Restricted Stock Units with Market Condition [Member]
Share-Based Compensation
Compensation Cost	$ 200,000
Maximum [Member] \| 2006 Stock Option Plan [Member] \| Stock Options [Member]
Share-Based Compensation
Expiration period	10 years
Vesting period	4 years
Maximum [Member] \| 2014 Stock Option Plan [Member] \| Stock Options [Member]
Share-Based Compensation
Expiration period	10 years
Vesting period	4 years

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - 2006 and 2014 Stock Option Plans [Member] - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2016
Share-Based Compensation
Number of Shares Outstanding, beginning of the period	3,785,083
Number of Shares, Granted	1,303,750
Number of Shares, Exercised	(21,014)
Number of Shares, Forfeited	(503,693)
Number of Shares, Cancelled	(22,044)
Number of Shares Outstanding, end of the period	4,542,082
Number of Shares, Exercisable	2,431,162
Number of Shares, Vested or expected to vest	4,046,752
Weighted-Average Exercise Price Per Share Outstanding, beginning of the period	$ 7.31
Weighted-Average Exercise Price Per Share, Granted	5.47
Weighted-Average Exercise Price Per Share, Exercised	3.21
Weighted-Average Exercise Price Per Share, Forfeited	6.56
Weighted-Average Exercise Price Per Share, Cancelled	14.07
Weighted-Average Exercise Price Per Share Outstanding, end of the period	6.85
Weighted-Average Exercise Price Per Share, Exercisable	7.30
Weighted-Average Exercise Price Per Share, Vested or expected to vest	$ 6.98
Weighted-Average Remaining Contractual Term, Outstanding	7 years 1 month 6 days	6 years 10 months 17 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 1 month 13 days
Weighted-Average Remaining Contractual Term, Vested or expected to vest	6 years 9 months 14 days
Aggregate Intrinsic Value, Outstanding, beginning of the period	$ 1,989
Aggregate Intrinsic Value, Exercised	51
Aggregate Intrinsic Value Outstanding, end of the period	6,824
Aggregate Intrinsic Value, Exercisable	4,816
Aggregate Intrinsic Value, Vested or expected to vest	$ 6,315

Stock-Based Compensation - Schedule of Estimated Assumptions Used to Calculate Weighted-Average Grant Date Fair Value of Options Granted (Detail) - Stock Options [Member] - 2006 and 2014 Stock Option Plans [Member]	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-Based Compensation
Weighted-average risk-free interest rate	2.63%	2.02%
Expected dividend yield	0.00%	0.00%
Expected volatility	68.00%	63.00%
Expected terms	6 years	6 years

Stock-Based Compensation - Schedule of Nonvested Restricted Stock Units Activity (Detail) - Restricted Stock Units [Member]	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Share-Based Compensation
Number of Shares, Nonvested restricted shares at the beginning of the period \| shares	606,497
Number of Shares, Restricted shares granted \| shares	1,217,189
Number of Shares, Restricted shares vested \| shares	(64,772)
Number of Shares, Restricted shares forfeited \| shares	(44,451)
Number of Shares, Cancelled \| shares	0
Number of Shares, Nonvested restricted shares at the end of the period \| shares	1,714,463
Weighted-Average Grant Date Fair Value, Nonvested restricted shares at the beginning of the period \| $ / shares	$ 5.23
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	5.06
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	5.82
Weighted-Average Grant Date Fair Value, Forfeited \| $ / shares	5.72
Weighted-Average Grant Date Fair Value, Cancelled \| $ / shares	0
Weighted-Average Grant Date Fair Value, Nonvested restricted shares at the end of the period \| $ / shares	$ 5.08

Stock-Based Compensation - Summary of Stock-Based Compensation Expense for Stock Options Granted that was Recorded in the Company's Results of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation expense
Stock-based compensation expense	$ 1,357	$ 1,128
Cost of Product Revenue [Member]
Stock-based compensation expense
Stock-based compensation expense	22	30
Research and Development [Member]
Stock-based compensation expense
Stock-based compensation expense	369	302
Selling, General and Administrative [Member]
Stock-based compensation expense
Stock-based compensation expense	$ 966	$ 796

Warrants - Additional Information (Detail) - Common Stock [Member] $ / shares in Units, $ in Millions	1 Months Ended
	Dec. 31, 2016 USD ($) Warrant $ / shares shares
Class of Warrant or Right [Line Items]
Number of warrants \| Warrant	4
Number of shares issuable for warrants outstanding \| shares	528,958
Exercise price of warrants \| $ / shares	$ 8.06
Fair market value of warrants \| $	$ 1.8

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	6,785,503	5,201,343
Options to Purchase Common Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	4,542,082	4,152,265
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	1,714,463	520,120
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	528,958	528,958

Co-Development Agreements - Additional Information (Detail)				1 Months Ended		3 Months Ended
	Nov. 01, 2016 USD ($) specie	Sep. 21, 2016 USD ($)	Feb. 03, 2015 USD ($) Item	Mar. 31, 2018 USD ($) Item specie	Oct. 31, 2015 USD ($)	Mar. 31, 2018 USD ($) Item	Mar. 31, 2017 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues						$ 2,311,000	$ 941,000
Co Development Partnership Agreement [Member] \| Canon U.S. Life Sciences Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment			$ 2,000,000
Additional consideration receivable upon achievement of certain development and regulatory milestones			6,500,000
Aggregate consideration receivable			$ 8,500,000
Proceeds received for achievement of milestone					$ 1,500,000
Additional consideration receivable upon achievement of additional development and regulatory milestones				$ 5,000,000		$ 5,000,000
Number of milestone payments \| Item				2		2
Additional consideration receivable upon achievement of development and regulatory milestones, payment one				$ 2,000,000		$ 2,000,000
Additional consideration receivable upon achievement of development and regulatory milestones, payment two				$ 3,000,000		3,000,000
Number of units \| Item			1
Revenues						0	300,000
Co Development Partnership Agreement [Member] \| Allergan Sales [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment	$ 2,000,000
Aggregate consideration receivable	$ 4,000,000
Revenues						1,300,000	$ 38,000
Number of additional bacteria species added to existing product candidate \| specie	1
Co Development Partnership Agreement [Member] \| CARB-X [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of additional bacteria species added to existing product candidate \| specie				20
Co Development Partnership Agreement [Member] \| CARB-X [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate consideration receivable				$ 2,000,000		$ 2,000,000
Collaborative arrangement reimbursement amount				1,100,000
Milestone payment				$ 900,000
Private Placement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from sale of shares in related party		$ 39,700,000
Percentage of outstanding shares at date of sale		19.90%