Merrimack Pharmaceuticals (MACK) 10-Q 11 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Entity Registrant Name	'MERRIMACK PHARMACEUTICALS INC	'
Entity Central Index Key	'0001274792	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	104,587,587

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$77,751	$65,086
Available-for-sale securities	14,995	90,116
Restricted cash	101	101
Accounts receivable	6,605	5,857
Prepaid expenses and other current assets	4,396	5,484
Total current assets	103,848	166,644
Restricted cash	584	584
Property and equipment, net	13,731	13,364
Other assets	160	175
Intangible assets, net	1,685	1,845
In-process research and development	6,200	6,200
Goodwill	3,605	3,605
Total assets	129,813	192,417
Current liabilities:	'	'
Accounts payable, accrued expenses and other	32,208	38,814
Deferred revenues	46,283	9,336
Deferred rent	1,310	1,336
Long-term debt, current portion	11,052	8,248
Total current liabilities	90,853	57,734
Deferred revenues, net of current portion	3,023	66,139
Deferred rent, net of current portion	5,987	6,538
Deferred tax incentives, net of current portion	740	507
Long-term debt, net of current portion	105,135	103,427
Accrued interest	1,200	1,200
Total liabilities	206,938	235,545
Commitments and contingencies (Note 10)	'	'
Non-controlling interest	-13	337
Stockholders' deficit:	'	'
Preferred stock, $0.01 par value: 10,000 shares authorized at June 30, 2014 and December 31, 2013; no shares issued or outstanding at June 30, 2014 or December 31, 2013	'	'
Common stock, $0.01 par value: 200,000 shares authorized at June 30, 2014 and December 31, 2013; 104,513 and 102,523 shares issued and outstanding at June 30, 2014 and December 31, 2013, respectively	1,045	1,025
Additional paid-in capital	539,785	527,779
Accumulated other comprehensive loss	-3	-24
Accumulated deficit	-617,939	-572,245
Total stockholders' deficit	-77,112	-43,465
Total liabilities, non-controlling interest and stockholders' deficit	$129,813	$192,417

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Preferred stock, par value	$0.01	$0.01
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	104,513	102,523
Common stock, shares outstanding	104,513	102,523

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Comprehensive Loss (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]	'	'	'	'
Collaboration revenues	$27,815	$18,452	$40,849	$33,107
Operating expenses:	'	'	'	'
Research and development	33,795	42,465	64,119	79,454
General and administrative	7,921	5,095	14,145	10,027
Total operating expenses	41,716	47,560	78,264	89,481
Loss from operations	-13,901	-29,108	-37,415	-56,374
Other income and expenses	'	'	'	'
Interest income	20	35	55	87
Interest expense	-4,570	-1,293	-9,081	-2,513
Other, net	161	115	397	226
Net loss	-18,290	-30,251	-46,044	-58,574
Less net loss attributable to non-controlling interest	-181	-169	-350	-339
Net loss attributable to Merrimack Pharmaceuticals, Inc.	-18,109	-30,082	-45,694	-58,235
Other comprehensive income:	'	'	'	'
Unrealized gain on available-for-sale securities	5	15	21	33
Other comprehensive income	5	15	21	33
Comprehensive loss	($18,104)	($30,067)	($45,673)	($58,202)
Net loss per share available to common stockholders-basic and diluted	($0.17)	($0.31)	($0.44)	($0.61)
Weighted-average common shares used in computing net loss per share available to common stockholders-basic and diluted	103,809	96,170	103,351	96,025

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities	'	'
Net loss	($46,044)	($58,574)
Adjustments to reconcile net loss to net cash used in operating activities	'	'
Non-cash interest expense	4,267	470
Depreciation and amortization	2,241	1,319
Stock-based compensation	7,091	5,416
Changes in operating assets and liabilities	'	'
Purchased premiums and interest on available-for-sale securities	-4	-291
Accounts receivable	-748	-5,270
Accounts payable, accrued expenses and other	-6,027	11,386
Deferred revenues	-26,169	-2,404
Other assets and liabilities, net	1,173	2,518
Net cash used in operating activities	-64,220	-45,430
Cash flows from investing activities	'	'
Purchases of available-for-sale securities	-20,100	-8,290
Proceeds from maturities of available-for-sale securities	94,733	49,010
Purchases of property and equipment	-2,983	-3,305
Other investing activities, net	'	-39
Net cash provided by investing activities	71,650	37,376
Cash flows from financing activities	'	'
Proceeds from exercise of common stock options and warrants	4,936	1,204
Proceeds from convertible notes issued by majority owned subsidiary, net of issuance costs	300	274
Other financing activities, net	-1	-195
Net cash provided by financing activities	5,235	1,283
Net increase (decrease) in cash and cash equivalents	12,665	-6,771
Cash and cash equivalents, beginning of period	65,086	37,714
Cash and cash equivalents, end of period	77,751	30,943
Non-cash investing and financing activities	'	'
Issuance of derivative liability	37	35
Property and equipment in accounts payable and accrued expenses	564	'
Disposal of fully depreciated assets	670	77
Supplemental disclosure of cash flows	'	'
Cash paid for interest	$4,915	$2,076

Nature_of_the_Business

Nature of the Business	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Nature of the Business	'
	1. Nature of the Business
	Merrimack Pharmaceuticals, Inc. (the “Company”) is a biopharmaceutical company discovering, developing and preparing to commercialize innovative medicines consisting of novel therapeutics paired with companion diagnostics for the treatment of cancer. The Company has six novel therapeutic oncology candidates in clinical development (MM-398, MM-121, MM-111, MM-302, MM-151 and MM-141), multiple product candidates in preclinical development and a discovery effort advancing additional candidate medicines. The Company also has an agreement to utilize its manufacturing expertise to develop, manufacture and exclusively supply bulk drug to a third party, who will in turn process the drug into a finished product and commercialize it globally. The Company’s discovery and development efforts are driven by Network Biology, which is its proprietary systems biology-based approach to biomedical research. The Company was incorporated in the Commonwealth of Massachusetts in 1993 and reincorporated in the State of Delaware in October 2010.
	The Company is subject to risks and uncertainties common to companies in the biopharmaceutical industry, including, but not limited to, its ability to secure additional capital to fund operations, success of clinical trials, development by competitors of new technological innovations, dependence on collaborative arrangements, protection of proprietary technology, compliance with government regulations and dependence on key personnel. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel, infrastructure and extensive compliance reporting capabilities.
	The Company has incurred significant losses and has not generated revenue from commercial sales. The accompanying condensed consolidated financial statements have been prepared on a basis which assumes that the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the normal course of business.
	As of June 30, 2014, the Company had unrestricted cash and cash equivalents and available-for-sale securities of $92.7 million. The Company expects that its existing unrestricted cash and cash equivalents and available-for-sale securities as of June 30, 2014, anticipated interest income and remaining funding under its license and collaboration agreement with Sanofi related to MM-121, which will terminate effective December 17, 2014 unless the Company chooses to accelerate such termination date, will enable the Company to fund operations into 2015.
	The Company may seek additional funding through public or private debt or equity financings, or through existing or new collaboration arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into additional collaborative arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Arrangements with collaborators or others may require the Company to relinquish rights to certain of its technologies or product candidates. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs or commercialization efforts, which could adversely affect its business prospects.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	2. Summary of Significant Accounting Policies
	Significant accounting policies followed by the Company in the preparation of its condensed consolidated financial statements are as follows:
	Basis of Presentation and Consolidation
	The accompanying condensed consolidated financial statements as of June 30, 2014, and for the three and six months ended June 30, 2014 and 2013, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all adjustments which are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These 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, 2013 filed with the SEC on March 4, 2014.
	The information presented in the condensed consolidated financial statements and related notes as of June 30, 2014, and for the three and six months ended June 30, 2014 and 2013, is unaudited. The December 31, 2013 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements.
	Interim results for the three and six months ended June 30, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2014, or any future period.
	These condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Merrimack Pharmaceuticals (Bermuda) Ltd. The Company also consolidates its majority owned subsidiary, Silver Creek Pharmaceuticals, Inc. (“Silver Creek”). All intercompany transactions and balances have been eliminated in consolidation.
	The Company’s ownership of Silver Creek was 64% as of June 30, 2014 and December 31, 2013. The consolidated financial statement activity related to Silver Creek was as follows:
	(in thousands)	Non-Controlling Interest
	Balance at December 31, 2013	$	337
	Net loss attributable to Silver Creek		(350	)
	Balance at June 30, 2014	$	(13	)
		Non-Controlling Interest
	Balance at December 31, 2012	$	97
	Net loss attributable to Silver Creek		(339	)
	Balance at June 30, 2013	$	(242	)
	In April 2014, Silver Creek named a new Chief Executive Officer and made changes to its board of directors. The Company remains the primary beneficiary of Silver Creek, so these changes to Silver Creek’s management and directors did not effect a change on the consolidation of Silver Creek for financial reporting purposes.
	Use of Estimates
	GAAP requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The most significant estimates in these condensed consolidated financial statements include revenue recognition, including the estimated percentage of billable expenses in any particular budget period, periods of meaningful use of licensed products, estimates used in accounting for revenue separability, accounting for revenue period of substantial involvement and recognition, useful lives with respect to long-lived assets and intangibles, accounting for stock-based compensation, contingencies, intangible assets, goodwill, in-process research and development, derivative liability, valuation of convertible debt, tax valuation reserves and accrued expenses, including clinical research costs. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management.
	Available-for-Sale Securities
	The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities may consist of U.S. government agencies securities, commercial paper, corporate notes and bonds and certificates of deposit, which are maintained by an investment manager. Available-for-sale securities are carried at fair value, with the unrealized gains and losses included in other comprehensive income as a component of stockholders’ deficit until realized. Realized gains and losses are recognized in interest income. Any premium or discount arising at purchase is amortized and/or accreted to interest income. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities during the three and six months ended June 30, 2014 or 2013.
	Available-for-sale securities, all of which have maturities of twelve months or less, as of June 30, 2014 consisted of the following:
		Amortized			Unrealized		Unrealized			Fair
		Cost			Gains		Losses			Value
		(in thousands)
	June 30, 2014:
	Commercial paper	$	14,998		$	—	$	(3	)	$	14,995
	The aggregate fair value of securities held by the Company in an unrealized loss position for less than 12 months as of June 30, 2014 was $15.0 million, which consisted of three commercial paper securities comprising the total balance. To determine whether an other-than-temporary impairment exists for securities with significant unrealized losses, the Company performs an analysis to assess whether it intends to sell, or whether it would more likely than not be required to sell, the security before the expected recovery of the amortized cost basis. Where the Company intends to sell a security, or may be required to do so, the security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is recognized on the statement of comprehensive loss as an other-than-temporary impairment charge. When this is not the case, the Company performs additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified when the Company does not expect to receive cash flows, based on using a single best estimate, sufficient to recover the amortized cost basis of a security, and the amount of the loss is recognized in other income (expense).
	The Company does not intend to sell, and it is not more likely than not that the Company will be required to sell, the above investments before the recovery of their amortized cost bases, which may occur upon maturity. The Company determined that there was no material change in the credit risk of the above investments. As a result, the Company determined it did not hold any investments with an other-than-temporary-impairment as of June 30, 2014.
	Concentration of Credit Risk
	Financial instruments that subject the Company to credit risk consist primarily of cash and cash equivalents, available-for-sale securities and accounts receivable. The Company places its cash deposits in accredited financial institutions and, therefore, the Company’s management believes these funds are subject to minimal credit risk. The Company invests cash equivalents and available-for-sale securities in money market funds, U.S. government agencies securities and various corporate debt securities. Credit risk in these securities is reduced as a result of the Company’s investment policy to limit the amount invested in any one issue or any single issuer and to only invest in high credit quality securities. The Company has no significant off-balance sheet concentrations of credit risk such as foreign currency exchange contracts, option contracts or other hedging arrangements.
	Revenue Recognition
	The Company enters into biopharmaceutical product development agreements with collaborative partners for the research and development of therapeutic and diagnostic products. The terms of the agreements may include nonrefundable signing and licensing fees, funding for research, development and manufacturing, milestone payments and royalties or profit-sharing on any product sales derived from collaborations. These multiple element arrangements are analyzed to determine whether the deliverables can be separated or whether they must be accounted for as a single unit of accounting.
	In January 2011, the Company adopted authoritative guidance on revenue recognition for multiple element arrangements. This guidance, which applies to multiple element arrangements entered into or materially modified on or after January 1, 2011, separates and allocates consideration in a multiple element arrangement according to the relative selling price of each deliverable. The fair value of deliverables under the arrangement may be derived using a best estimate of selling price if vendor specific objective evidence and third-party evidence are not available. Deliverables under the arrangement will be separate units of accounting provided that a delivered item has value to the customer on a stand-alone basis and if the arrangement does not include a general right of return relative to the delivered item and delivery or performance of the undelivered item is considered probable and substantially in the control of the vendor.
	The Company entered into a collaboration agreement with Watson Laboratories, Inc. (“Actavis”) in November 2013, which was evaluated under the accounting guidance on revenue recognition for multiple element arrangements. See Note 4, “License and Collaboration Agreements,” for additional information.
	The Company’s license and collaboration agreements executed prior to January 1, 2011 continue to be accounted for under previously issued revenue recognition guidance for multiple element arrangements. The Company recognized upfront license payments as revenue upon delivery of the license only if the license had stand-alone value and the fair value of the undelivered performance obligations could be determined. If the fair value of the undelivered performance obligations could be determined, such obligations were accounted for separately as the obligations were fulfilled. If the license was considered to either not have stand-alone value or have stand-alone value but the fair value of any of the undelivered performance obligations could not be determined, the arrangement was accounted for as a single unit of accounting and the license payments and payments for performance obligations were recognized as revenue over the estimated period of when the performance obligations would be performed.
	Whenever the Company determined that an arrangement should be accounted for as a single unit of accounting, it determined the period over which the performance obligations would be performed and revenue would be recognized. If the Company could not reasonably estimate the timing and the level of effort to complete its performance obligations under the arrangement, then revenue under the arrangement was recognized on a straight-line basis over the period the Company expected to complete its performance obligations, which is reassessed at each subsequent reporting period.
	The Company’s collaboration agreements may include additional payments upon the achievement of performance-based milestones. As milestones are achieved, a portion of the milestone payment, equal to the percentage of the total time that the Company has performed the performance obligations to date over the total estimated time to complete the performance obligations, multiplied by the amount of the milestone payment, will be recognized as revenue upon achievement of such milestone. The remaining portion of the milestone will be recognized over the remaining performance period. Milestones that are tied to regulatory approvals are not considered probable of being achieved until such approval is received. Milestones tied to counterparty performance are not included in the Company’s revenue model until the performance conditions are met.
	Royalty revenue will be recognized upon the sale of the related products provided the Company has no remaining performance obligations under the arrangement.
	The Company did not materially modify any of its previously-existing multiple element arrangements during the six months ended June 30, 2014 and 2013 other than as discussed in Note 4, “License and Collaboration Agreements.”
	Stock-Based Compensation
	The Company expenses the fair value of employee stock options over the vesting period. Compensation expense is measured using the fair value of the award at the grant date, net of estimated forfeitures, and is adjusted annually to reflect actual forfeitures. The fair value of each stock-based award is estimated using the Black-Scholes option valuation model and is expensed straight-line over the vesting period.
	The Company records stock options issued to non-employees at fair value, periodically remeasures to reflect the current fair value at each reporting period, and recognizes expense over the related service period. When applicable, these equity instruments are accounted for based on the fair value of the consideration received or the fair value of the equity instrument issued, whichever is more reliably measurable.
	Other Income and Expense
	The Company records gains and losses on the recognition of federal and state sponsored tax incentives and other one-time income or expense-related items in other income (expense).
	In May 2014, the Company received an award of $0.6 million of tax incentives from the Massachusetts Life Sciences Center, which allows the Company to monetize approximately $0.6 million of state research and development tax credits. In exchange for these incentives, the Company pledged to hire an incremental 31 employees and to maintain the additional headcount through at least December 31, 2018. Failure to do so could result in the Company being required to repay some or all of these incentives. The Company has deferred and will amortize the benefit of this monetization on a straight-line basis over the five-year performance period, commencing with a cumulative catch-up when the pledge is achieved.
	Recent Accounting Pronouncements
	In July 2013, the Financial Accounting Standards Board (“FASB”) issued guidance to address the diversity in practice related to the financial statement presentation of unrecognized tax benefits as either a reduction of a deferred tax asset or a liability when a net operating loss carryforward, a similar tax loss or a tax credit carryforward exists. This guidance was effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.
	In May 2014, the FASB issued guidance which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. This guidance will be effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2016, and early adoption is not permitted. The Company is currently evaluating the potential impact that the adoption of this guidance and the related transition guidance may have on the consolidated financial statements.

Net_Loss_Per_Common_Share

Net Loss Per Common Share	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Net Loss Per Common Share	'
	3. Net Loss Per Common Share
	Basic net loss per share is calculated by dividing the net loss available to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing the net loss available to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method.
	As discussed in Note 7, “Borrowings,” in July 2013, the Company issued $125.0 million aggregate principal amount of 4.50% convertible senior notes due 2020 (the “Notes”) in an underwritten public offering. Upon any conversion of the Notes while the Company has indebtedness outstanding under the Loan and Security Agreement (the “Loan Agreement”) with Hercules Technology Growth Capital, Inc. (“Hercules”), the Notes will be settled in shares of the Company’s common stock. Following the repayment and satisfaction in full of the Company’s obligations to Hercules under the Loan Agreement, upon any conversion of the Notes, the Notes may be settled, at the Company’s election, in cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock. For purposes of calculating the maximum dilutive impact, it is presumed that the conversion premium will be settled in common stock, inclusive of a contractual make-whole provision resulting from a fundamental change, and the resulting potential common shares included in diluted earnings per share if the effect is more dilutive. For purposes of this calculation, conversion of the Notes, stock options and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The stock options, warrants and conversion premium on the Notes are excluded from the calculation of diluted loss per share because the net loss for the three and six months ended June 30, 2014 and 2013 causes such securities to be anti-dilutive. The potential dilutive effect of these securities is shown in the chart below:
		As of June 30,
	(in thousands)	2014		2013
	Options to purchase common stock		21,245		20,447
	Common stock warrants		2,407		2,777
	Conversion premium on the Notes		25,000		—

License_and_Collaboration_Agre

License and Collaboration Agreements	6 Months Ended
	Jun. 30, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
License and Collaboration Agreements	'
	4. License and Collaboration Agreements
	Sanofi
	On September 30, 2009, the Company entered into a license and collaboration agreement with Sanofi for the development and commercialization of a drug candidate being developed by the Company under the name MM-121. The agreement became effective on November 10, 2009 and Sanofi paid the Company a nonrefundable, noncreditable upfront license fee of $60.0 million. From the effective date of the agreement through June 30, 2014, the Company has received total milestone payments of $25.0 million pursuant to the agreement. Under the agreement, Sanofi is responsible for all MM-121 development and manufacturing costs. Sanofi reimburses the Company for direct costs incurred in both development and manufacturing and compensates the Company for its internal development efforts based on a full time equivalent rate.
	On June 17, 2014, the Company and Sanofi agreed to terminate the license and collaboration agreement effective December 17, 2014, although the Company has the right to accelerate such termination date. In connection with the agreement to terminate the collaboration, among other things, Sanofi transferred ownership of the investigational new drug application for MM-121 back to the Company in July 2014, and the Company waived Sanofi’s obligation to reimburse Merrimack for MM-121 development costs incurred after the effective termination date. Effective upon the termination of the license and collaboration agreement, the Company will not be entitled to receive any additional fees, milestone payments or reimbursements from the collaboration.
	The Company recognizes cost reimbursements for MM-121 development services within the period they are incurred and billable. Billable expenses are identified during each specified budget period. For the three and six months ended June 30, 2014, this specified budget period was prospectively determined to end December 17, 2014, although the specified allowable budget expense was not changed. In the event that total development services expense incurred and expected to be incurred during the same period exceed the total contractually allowed billable amount for development services during that period, the Company recognizes only a percentage of the development services incurred as revenue during that period. This percentage is calculated as total development services expense incurred during the specified budget period divided by the sum of total development services expense incurred plus estimated development services expense to be incurred during the specified period, multiplied by the total contractually allowed billable amount for development services during the specified period, less development services revenue previously recognized within the specified period.
	At the inception of the collaboration, the Company determined that the license, the right to future technology, back-up compounds, participation on steering committees and manufacturing services performance obligations comprising the license and collaboration agreement represented a single unit of accounting. As the Company cannot reasonably estimate its level of effort over the collaboration, the Company recognizes revenue from the upfront payment, milestone payment and manufacturing services payments using the contingency-adjusted performance model over the expected development period, which was initially estimated at 12 years from the effective date of the agreement.
	As a result of the Company and Sanofi agreeing to terminate the license and collaboration arrangement, the development period was revised to end as of December 17, 2014. Accordingly, the balance of the deferred revenue remaining on April 1, 2014 is being recognized prospectively on a straight-line basis over the remaining development period, estimated to end on December 17, 2014, in accordance with current generally accepted principles on revenue recognition.
	During the three and six months ended June 30, 2014 and 2013, the Company recognized revenue based on the following components of the Sanofi agreement:
		Three months ended				Six months ended
		June 30,				June 30,
	(in thousands)	2014		2013		2014		2013
	Upfront payment	$	13,268	$	1,250	$	14,518	$	2,500
	Milestone payments		5,529		521		6,049		1,042
	Development services		3,040		14,682		13,740		26,272
	Manufacturing services and other		5,978		1,999		6,542		2,740
	Total	$	27,815	$	18,452	$	40,849	$	32,554
	The Company performs development services for which revenue is recognized under the Sanofi agreement in accordance with the specified budget period. Additionally, for the six months ended June 30, 2014, there is approximately $5.8 million of increased revenue related to the Company receiving budget approval for expenses incurred prior to December 31, 2013.
	As of June 30, 2014 and December 31, 2013, the Company maintained the following assets and liabilities related to the Sanofi agreement:
	(in thousands)	June 30, 2014		December 31, 2013
	Accounts receivable, billed	$	3,390	$	2,357
	Accounts receivable, unbilled		2,938		3,417
	Deferred revenue		46,283		73,392
	PharmaEngine, Inc.
	On May 5, 2011, the Company entered into an assignment, sublicense and collaboration agreement with PharmaEngine, Inc. (“PharmaEngine”) under which the Company reacquired rights in Europe and certain countries in Asia to a drug being developed under the name MM-398. In exchange, the Company agreed to pay PharmaEngine a nonrefundable, noncreditable upfront payment of $10.0 million and will be required to make up to an aggregate of $80.0 million in development and regulatory milestone payments and $130.0 million in sales milestone payments upon the achievement of specified development, regulatory and annual net sales milestones. During the first quarter of 2012, the Company paid a milestone of $5.0 million under the collaboration agreement with PharmaEngine in connection with dosing the first patient in a Phase 3 clinical trial of MM-398 in pancreatic cancer. PharmaEngine is also entitled to tiered royalties on net sales of MM-398 in Europe and certain countries in Asia. The Company is responsible for all future development costs of MM-398 except those required specifically for regulatory approval in Taiwan.
	During the three months ended June 30, 2014 and 2013, the Company recognized research and development expenses of $0.1 million and $0.2 million, respectively, and during the six months ended June 30, 2014 and 2013, the Company recognized research and development expenses of $0.2 million and $0.5 million, respectively, related to the agreement with PharmaEngine.
	Actavis
	On November 25, 2013, the Company and Actavis entered into a development, license and supply agreement pursuant to which the Company will develop, manufacture and exclusively supply the bulk form of doxorubicin HCl liposome injection (the “Initial Product”) to Actavis. Under the agreement, Actavis is responsible for all costs related to finished product processing and global commercialization. Pursuant to the agreement, the Company has also agreed to develop additional products for Actavis in the future, the identities of which will be mutually agreed upon. The Company is eligible to receive up to $15.5 million under the agreement, of which $2.7 million has been received through June 30, 2014, with the remainder relating to development funding and development, regulatory and commercial milestone payments related to the Initial Product. The Company will also receive a double digit share of net profits on global sales of the Initial Product and any additional products. The Company will manufacture and supply the Initial Product to Actavis in bulk form at an agreed upon unit price.
	The agreement will expire with respect to the Initial Product and any additional products developed in the future ten years after Actavis’ first sale of the applicable product, unless terminated earlier, and will automatically renew for additional two year periods thereafter unless either party provides notice of non-renewal. Either party may terminate the agreement in the event of an uncured material breach or bankruptcy filing by the other party. Actavis may also terminate the agreement for convenience in specified circumstances upon 90 days’ prior written notice.
	The Company applied revenue recognition guidance to determine whether the performance obligations under this collaboration, including the license, participation on steering committees, development services, and manufacturing and supply services could be accounted for separately or as a single unit of accounting. The Company determined that these obligations represent a single unit of accounting and will recognize revenue as product is supplied to Actavis. Therefore, the Company has deferred total billed and billable milestones and development expenses of $3.0 million as of June 30, 2014 and $2.1 million as of December 31 2013 related to the agreement.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	5. Fair Value of Financial Instruments
	The carrying value of financial instruments, including cash and cash equivalents, restricted cash, available-for-sale securities, prepaid expenses, accounts receivable, accounts payable and accrued expenses, and other short-term assets and liabilities approximate their respective fair values due to the short-term maturities of these assets and liabilities.
	Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value.
	Recurring Fair Value Measurements
	The following tables show assets and liabilities measured at fair value on a recurring basis as of June 30, 2014 and December 31, 2013 and the input categories associated with those assets and liabilities:
	As of June 30, 2014	Level 1		Level 2		Level 3
	(in thousands)
	Assets:
	Cash equivalents – money market funds	$	67,108	$	—	$	—
	Investments – commercial paper		—		14,995		—
	As of December 31, 2013	Level 1		Level 2		Level 3
	(in thousands)
	Assets:
	Cash equivalents – money market funds	$	47,740	$	—	$	—
	Cash equivalents – corporate debt securities		—		13,998		—
	Investments – commercial paper		—		49,680		—
	Investments – corporate debt securities		—		40,436		—
	The Company’s investment portfolio consists of investments classified as cash equivalents and available-for-sale securities. All highly liquid investments with an original maturity of three months or less when purchased are considered to be cash equivalents. The Company’s cash and cash equivalents are invested in U.S. treasury and various corporate debt securities that approximate their face value. All marketable securities with an original maturity when purchased of greater than three months are classified as available-for-sale. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in other comprehensive income. The amortized cost of securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity.
	Other Fair Value Measurements
	The estimated fair value of the $125.0 million aggregate principal amount of the Notes was $170.2 million as of June 30, 2014. The Company estimated the fair value of the Notes by using a quoted market rate in an inactive market, which is classified as a Level 2 input. The carrying value of the Notes is $76.6 million due to the bifurcation of the conversion feature of the Notes as described more fully in Note 7, “Borrowings.”
	The estimated fair value and carrying value of the loans payable under the Loan Agreement with Hercules was $39.6 million and $40.5 million, respectively, as of June 30, 2014. The Company estimated the fair value of the loans payable by using publically available information related to Hercules’ portfolio of debt investments based on unobservable inputs, which is classified as a Level 3 input.
	The immaterial fair value of a derivative liability as of June 30, 2014 was determined using a probability-weighted valuation based upon the likelihood of Silver Creek achieving a qualified financing, which is classified as a Level 3 input, as described in Note 7, “Borrowings.”

Accounts_Payable_Accrued_Expen

Accounts Payable, Accrued Expenses and Other	6 Months Ended
	Jun. 30, 2014
Payables And Accruals [Abstract]	'
Accounts Payable, Accrued Expenses and Other	'
	6. Accounts Payable, Accrued Expenses and Other
	Accounts payable, accrued expenses and other as of June 30, 2014 and December 31, 2013 consisted of the following:
	(in thousands)	June 30, 2014		December 31, 2013
	Accounts payable	$	4,320	$	1,889
	Accrued goods and services		19,075		26,031
	Accrued payroll and related benefits		5,207		7,255
	Accrued interest		2,945		2,926
	Accrued dividends payable		25		25
	Deferred tax incentives		636		688
	Total accounts payable, accrued expenses and other	$	32,208	$	38,814

Borrowings

Borrowings	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Borrowings	'
	7. Borrowings
	Future minimum payments under indebtedness agreements outstanding as of June 30, 2014 are as follows:
	As of June 30, 2014:	4.50% Convertible			Loan
	(in thousands)	Senior Notes			Agreement
	Remainder of 2014	$	2,813		$	5,626
	2015		5,625			18,135
	2016		5,625			23,804
	2017		5,625			—
	2018 and thereafter		141,875			—
		$	161,563		$	47,565
	Less interest		(36,563	)		(6,365	)
	Less unamortized discount		(48,413	)		(1,862	)
	Less current portion		—			(10,790	)
	Loans payable, net of current portion	$	76,587		$	28,548
	4.50% Convertible Senior Notes
	In July 2013, the Company issued $125.0 million aggregate principal amount of Notes in an underwritten public offering. As a result of the Notes offering, the Company received net proceeds of approximately $120.6 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company.
	The Notes bear interest at a rate of 4.50% per year, payable semiannually in arrears on January 15 and July 15 of each year, beginning on January 15, 2014. The Notes are general unsecured senior obligations of the Company.
	The Notes will mature on July 15, 2020 (the “Maturity Date”), unless earlier repurchased by the Company or converted at the option of holders. Holders may convert their Notes at their option at any time prior to the close of business on the business day immediately preceding April 15, 2020 only under certain circumstances. Upon any conversion of Notes that occurs while the Company’s indebtedness to Hercules under the Loan Agreement remains outstanding, the Notes will be settled in shares of the Company’s common stock. Following the repayment and satisfaction in full of the Company’s obligations to Hercules under the Loan Agreement, upon any conversion of the Notes, the Notes may be settled, at the Company’s election, in cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock.
	The initial conversion rate of the Notes is 160 shares of the Company’s common stock per $1,000 principal amount of Notes, which is equivalent to an initial conversion price of $6.25 per share of common stock. The conversion rate will be subject to adjustment in some events. In addition, following certain corporate events that occur prior to the Maturity Date, the Company will increase the conversion rate for a holder who elects to convert its Notes in connection with such a corporate event in certain circumstances.
	The Company has separately accounted for the liability and equity components of the Notes by bifurcating gross proceeds between the indebtedness, or liability component, and the embedded conversion option, or equity component. This bifurcation was done by estimating an effective interest rate as of the date of issuance for similar notes which do not contain an embedded conversion option. The embedded conversion option was recorded in stockholders’ deficit and as debt discount, to be subsequently amortized as interest expense over the term of the Notes. Underwriting discounts and commissions and offering expenses totaled $4.4 million and were allocated to the indebtedness and the embedded conversion option based on their relative values.
	For the three and six months ended June 30, 2014, interest expense related to the outstanding principal balance of the Notes was $3.4 million and $6.8 million, respectively.
	Loan Agreement
	In November 2012, the Company entered into the Loan Agreement with Hercules pursuant to which the Company received loans in the aggregate principal amount of $40.0 million in 2012. The Company, as permitted under the Loan Agreement, had previously extended the interest-only payment period with the aggregate principal balance of the loans to be repaid in monthly installments starting on June 1, 2014 and continuing through November 1, 2016. On June 25, 2014, the Company entered into an amendment to the Loan Agreement, whereby the Company and Hercules agreed to extend by four additional months the period during which the Company makes interest-only payments. As a result of the amendment, the Company will repay the aggregate outstanding principal balance of the loan in equal monthly installments of principal and interest (based on a 30 month amortization schedule) beginning on October 1, 2014. The remaining principal balance and interest will be due and payable on November 1, 2016.
	Upon full repayment or maturity of the loans, the Company is required to pay Hercules a fee of $1.2 million, which has been recorded as a discount to the loans and as a long-term liability on the Company’s condensed consolidated balance sheets. Additionally, the Company reimbursed Hercules for costs incurred related to the loans, which has been reflected as a discount to the carrying value of the loans. The Company is amortizing these loan discounts totaling $1.6 million to interest expense over the term of the loans using the effective interest method. For the three months and six months ended June 30, 2014, interest expense related to Hercules loans payable was $1.2 million and $2.4 million, respectively. For the three and six months ended June 30, 2013, interest expense related to Hercules loans payable was also $1.2 million and $2.4 million, respectively.
	In connection with the Loan Agreement, the Company granted Hercules a security interest in all of the Company’s personal property now owned or hereafter acquired, excluding intellectual property but including the proceeds from the sale, if any, of intellectual property, and a negative pledge on intellectual property. The Loan Agreement also contains certain representations, warranties and non-financial covenants of the Company.
	Convertible Notes - Silver Creek
	Between April and June 2014, the Company’s majority owned subsidiary, Silver Creek, issued an aggregate of $0.3 million in convertible notes to multiple legal entities pursuant to a Note Purchase Agreement. The notes bear interest at 6% and mature and convert, along with accrued interest, into Silver Creek Series A preferred stock on December 31, 2014. If at any time prior to maturity Silver Creek enters into a qualifying equity financing, defined as a sale or series of related sales of equity securities prior to the maturity date and resulting in at least $4.0 million of gross proceeds, the notes will automatically convert into the next qualifying equity financing at a 25% discount. The Company determined that this convertible feature met the definition of a derivative and required separate accounting treatment. The derivative was estimated to be immaterial upon issuance and as of June 30, 2014 using a probability-weighted model, and was recorded as derivative liability within other current liabilities on the consolidated balance sheets. As of June 30, 2014, Silver Creek had outstanding borrowings of $0.3 million, net of immaterial debt discounts. For the three and six months ended June 30, 2014, interest expense related to the outstanding principal balance under the Note Purchase Agreement was immaterial.

Common_Stock

Common Stock	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Common Stock	'
	8. Common Stock
	As of June 30, 2014 and December 31, 2013, the Company had 200.0 million shares of $0.01 par value common stock authorized. There were approximately 104,513,000 and 102,523,000 shares of common stock issued and outstanding as of June 30, 2014 and December 31, 2013, respectively.
	In February 2014, Hercules exercised warrants to purchase 302,143 shares of common stock for proceeds to the Company of $1.1 million.
	The shares reserved for future issuance as of June 30, 2014 and December 31, 2013 consisted of the following:
	(in thousands)	June 30, 2014		December 31, 2013
	Options to purchase common stock		21,245		20,107
	Common stock warrants		2,407		2,777
	Conversion premium on the Notes		25,000		25,000

StockBased_Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation	'
	9. Stock-Based Compensation
	As of December 31, 2013, there were 1.7 million shares of common stock available to be granted under the Company’s 2011 Stock Incentive Plan (the “2011 Plan”). The 2011 Plan is administered by the Company’s board of directors and permits the Company to grant incentive and non-qualified stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards.
	In January 2014, 3.6 million additional shares of common stock became available for grant to employees, officers, directors and consultants under the 2011 Plan. During the six months ended June 30, 2014 and 2013, the Company issued options to purchase 3.1 million and 3.0 million shares of common stock, respectively. At June 30, 2014, there were 2.5 million shares remaining available for grant under the 2011 Plan.
	The assumptions used to estimate the fair value of options granted to employees and directors at the date of grant for the three and six months ended June 30, 2014 were as follows:
		Three months ended			Six months ended
		June 30,			June 30,
		2014		2013	2014		2013
	Risk-free interest rate	1.6-1.9%		0.1-1.4%	1.6-1.9%		0.1-1.4%
	Expected dividend yield	0%		0%	0%		0%
	Expected term	5.0-5.9 years		5.3-5.9 years	5.0-5.9 years		5.3-5.9 years
	Expected volatility	64-70%		67-68%	64-70%		67-68%
	Options granted to directors during the three and six months ended June 30, 2014 vested immediately. Options granted to directors during the three and six months ended June 30, 2013 vested over a one year period. Options granted to employees generally vest over a three year period. The Company recognized stock-based compensation expense as follows for the three and six months ended June 30, 2014 and 2013:
		Three months ended						Six months ended
		June 30,						June 30,
	(in thousands)	2014			2013			2014		2013
	Employee awards:
	Research and development	$	1,841		$	1,651		$	3,522	$	2,935
	General and administrative		2,161			1,307			3,453		2,397
	Stock-based compensation for employee awards		4,002			2,958			6,975		5,332
	Stock-based compensation for non-employee awards		153			72			116		84
	Total stock-based compensation	$	4,155		$	3,030		$	7,091	$	5,416
	The following table summarizes stock option activity during the six months ended June 30, 2014:
	(in thousands, except per share amounts and years)	Number			Weighted			Weighted		Aggregate
		of			Average			Average		Intrinsic
		Shares			Exercise Price			Remaining		Value
								Contractual
								Term
	Outstanding, December 31, 2013		20,107		$	3.93			6.11	$	38,348
	Granted		3,107		$	5.17
	Exercised		(1,653	)	$	2.34
	Forfeited		(316	)	$	6.27
	Outstanding, June 30, 2014		21,245		$	4.2			6.29	$	66,353
	Vested and expected to vest, June 30, 2014		20,889		$	4.17			6.24	$	65,734
	Exercisable, June 30, 2014		15,759		$	3.62			5.35	$	58,220
	The aggregate intrinsic value was calculated as the difference between the exercise price of the stock options and the fair value of the underlying common stock.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	10. Commitments and Contingencies
	Operating Leases
	The Company leases its office, laboratory and manufacturing space under non-cancelable operating leases. Total rent expense under these operating leases was $1.5 million and $1.4 million for the three months ended June 30, 2014 and 2013, respectively. Total rent expense under these operating leases was $3.0 million and $2.6 million for the six months ended June 30, 2014 and 2013, respectively.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Basis of Presentation and Consolidation	'
	Basis of Presentation and Consolidation
	The accompanying condensed consolidated financial statements as of June 30, 2014, and for the three and six months ended June 30, 2014 and 2013, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all adjustments which are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These 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, 2013 filed with the SEC on March 4, 2014.
	The information presented in the condensed consolidated financial statements and related notes as of June 30, 2014, and for the three and six months ended June 30, 2014 and 2013, is unaudited. The December 31, 2013 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements.
	Interim results for the three and six months ended June 30, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2014, or any future period.
	These condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Merrimack Pharmaceuticals (Bermuda) Ltd. The Company also consolidates its majority owned subsidiary, Silver Creek Pharmaceuticals, Inc. (“Silver Creek”). All intercompany transactions and balances have been eliminated in consolidation.
	The Company’s ownership of Silver Creek was 64% as of June 30, 2014 and December 31, 2013. The consolidated financial statement activity related to Silver Creek was as follows:
		Non-Controlling Interest
		(Deficit)
	Balance at December 31, 2013	$	337
	Net loss attributable to Silver Creek		(350	)
	Balance at June 30, 2014	$	(13	)
	(in thousands)	Non-Controlling Interest
		(Deficit)
	Balance at December 31, 2012	$	97
	Net loss attributable to Silver Creek		(339	)
	Balance at June 30, 2013	$	(242	)
	In April 2014, Silver Creek named a new Chief Executive Officer and made changes to its board of directors. The Company remains the primary beneficiary of Silver Creek, so these changes to Silver Creek’s management and directors did not effect a change on the consolidation of Silver Creek for financial reporting purposes.
Use of Estimates	'
	Use of Estimates
	GAAP requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The most significant estimates in these condensed consolidated financial statements include revenue recognition, including the estimated percentage of billable expenses in any particular budget period, periods of meaningful use of licensed products, estimates used in accounting for revenue separability, accounting for revenue period of substantial involvement and recognition, useful lives with respect to long-lived assets and intangibles, accounting for stock-based compensation, contingencies, intangible assets, goodwill, in-process research and development, derivative liability, valuation of convertible debt, tax valuation reserves and accrued expenses, including clinical research costs. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management.
Available-for-Sale Securities	'
	Available-for-Sale Securities
	The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities may consist of U.S. government agencies securities, commercial paper, corporate notes and bonds and certificates of deposit, which are maintained by an investment manager. Available-for-sale securities are carried at fair value, with the unrealized gains and losses included in other comprehensive income as a component of stockholders’ deficit until realized. Realized gains and losses are recognized in interest income. Any premium or discount arising at purchase is amortized and/or accreted to interest income. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities during the three and six months ended June 30, 2014 or 2013.
	Available-for-sale securities, all of which have maturities of twelve months or less, as of June 30, 2014 consisted of the following:
		Amortized			Unrealized		Unrealized			Fair
		Cost			Gains		Losses			Value
		(in thousands)
	June 30, 2014:
	Commercial paper	$	14,998		$	—	$	(3	)	$	14,995
	The aggregate fair value of securities held by the Company in an unrealized loss position for less than 12 months as of June 30, 2014 was $15.0 million, which consisted of three commercial paper securities comprising the total balance. To determine whether an other-than-temporary impairment exists for securities with significant unrealized losses, the Company performs an analysis to assess whether it intends to sell, or whether it would more likely than not be required to sell, the security before the expected recovery of the amortized cost basis. Where the Company intends to sell a security, or may be required to do so, the security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is recognized on the statement of comprehensive loss as an other-than-temporary impairment charge. When this is not the case, the Company performs additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified when the Company does not expect to receive cash flows, based on using a single best estimate, sufficient to recover the amortized cost basis of a security, and the amount of the loss is recognized in other income (expense).
	The Company does not intend to sell, and it is not more likely than not that the Company will be required to sell, the above investments before the recovery of their amortized cost bases, which may occur upon maturity. The Company determined that there was no material change in the credit risk of the above investments. As a result, the Company determined it did not hold any investments with an other-than-temporary-impairment as of June 30, 2014.
Concentration of Credit Risk	'
	Concentration of Credit Risk
	Financial instruments that subject the Company to credit risk consist primarily of cash and cash equivalents, available-for-sale securities and accounts receivable. The Company places its cash deposits in accredited financial institutions and, therefore, the Company’s management believes these funds are subject to minimal credit risk. The Company invests cash equivalents and available-for-sale securities in money market funds, U.S. government agencies securities and various corporate debt securities. Credit risk in these securities is reduced as a result of the Company’s investment policy to limit the amount invested in any one issue or any single issuer and to only invest in high credit quality securities. The Company has no significant off-balance sheet concentrations of credit risk such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Revenue Recognition	'
	Revenue Recognition
	The Company enters into biopharmaceutical product development agreements with collaborative partners for the research and development of therapeutic and diagnostic products. The terms of the agreements may include nonrefundable signing and licensing fees, funding for research, development and manufacturing, milestone payments and royalties or profit-sharing on any product sales derived from collaborations. These multiple element arrangements are analyzed to determine whether the deliverables can be separated or whether they must be accounted for as a single unit of accounting.
	In January 2011, the Company adopted authoritative guidance on revenue recognition for multiple element arrangements. This guidance, which applies to multiple element arrangements entered into or materially modified on or after January 1, 2011, separates and allocates consideration in a multiple element arrangement according to the relative selling price of each deliverable. The fair value of deliverables under the arrangement may be derived using a best estimate of selling price if vendor specific objective evidence and third-party evidence are not available. Deliverables under the arrangement will be separate units of accounting provided that a delivered item has value to the customer on a stand-alone basis and if the arrangement does not include a general right of return relative to the delivered item and delivery or performance of the undelivered item is considered probable and substantially in the control of the vendor.
	The Company entered into a collaboration agreement with Watson Laboratories, Inc. (“Actavis”) in November 2013, which was evaluated under the accounting guidance on revenue recognition for multiple element arrangements. See Note 4, “License and Collaboration Agreements,” for additional information.
	The Company’s license and collaboration agreements executed prior to January 1, 2011 continue to be accounted for under previously issued revenue recognition guidance for multiple element arrangements. The Company recognized upfront license payments as revenue upon delivery of the license only if the license had stand-alone value and the fair value of the undelivered performance obligations could be determined. If the fair value of the undelivered performance obligations could be determined, such obligations were accounted for separately as the obligations were fulfilled. If the license was considered to either not have stand-alone value or have stand-alone value but the fair value of any of the undelivered performance obligations could not be determined, the arrangement was accounted for as a single unit of accounting and the license payments and payments for performance obligations were recognized as revenue over the estimated period of when the performance obligations would be performed.
	Whenever the Company determined that an arrangement should be accounted for as a single unit of accounting, it determined the period over which the performance obligations would be performed and revenue would be recognized. If the Company could not reasonably estimate the timing and the level of effort to complete its performance obligations under the arrangement, then revenue under the arrangement was recognized on a straight-line basis over the period the Company expected to complete its performance obligations, which is reassessed at each subsequent reporting period.
	The Company’s collaboration agreements may include additional payments upon the achievement of performance-based milestones. As milestones are achieved, a portion of the milestone payment, equal to the percentage of the total time that the Company has performed the performance obligations to date over the total estimated time to complete the performance obligations, multiplied by the amount of the milestone payment, will be recognized as revenue upon achievement of such milestone. The remaining portion of the milestone will be recognized over the remaining performance period. Milestones that are tied to regulatory approvals are not considered probable of being achieved until such approval is received. Milestones tied to counterparty performance are not included in the Company’s revenue model until the performance conditions are met.
	Royalty revenue will be recognized upon the sale of the related products provided the Company has no remaining performance obligations under the arrangement.
	The Company did not materially modify any of its previously-existing multiple element arrangements during the six months ended June 30, 2014 and 2013 other than as discussed in Note 4, “License and Collaboration Agreements.”
Stock-Based Compensation	'
	Stock-Based Compensation
	The Company expenses the fair value of employee stock options over the vesting period. Compensation expense is measured using the fair value of the award at the grant date, net of estimated forfeitures, and is adjusted annually to reflect actual forfeitures. The fair value of each stock-based award is estimated using the Black-Scholes option valuation model and is expensed straight-line over the vesting period.
	The Company records stock options issued to non-employees at fair value, periodically remeasures to reflect the current fair value at each reporting period, and recognizes expense over the related service period. When applicable, these equity instruments are accounted for based on the fair value of the consideration received or the fair value of the equity instrument issued, whichever is more reliably measurable.
Other Income and Expense	'
	Other Income and Expense
	The Company records gains and losses on the recognition of federal and state sponsored tax incentives and other one-time income or expense-related items in other income (expense).
	In May 2014, the Company received an award of $0.6 million of tax incentives from the Massachusetts Life Sciences Center, which allows the Company to monetize approximately $0.6 million of state research and development tax credits. In exchange for these incentives, the Company pledged to hire an incremental 31 employees and to maintain the additional headcount through at least December 31, 2018. Failure to do so could result in the Company being required to repay some or all of these incentives. The Company has deferred and will amortize the benefit of this monetization on a straight-line basis over the five-year performance period, commencing with a cumulative catch-up when the pledge is achieved.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In July 2013, the Financial Accounting Standards Board (“FASB”) issued guidance to address the diversity in practice related to the financial statement presentation of unrecognized tax benefits as either a reduction of a deferred tax asset or a liability when a net operating loss carryforward, a similar tax loss or a tax credit carryforward exists. This guidance was effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.
	In May 2014, the FASB issued guidance which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. This guidance will be effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2016, and early adoption is not permitted. The Company is currently evaluating the potential impact that the adoption of this guidance and the related transition guidance may have on the consolidated financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Schedule of Non-Controlling Interest in Subsidiary	'
	The Company’s ownership of Silver Creek was 64% as of June 30, 2014 and December 31, 2013. The consolidated financial statement activity related to Silver Creek was as follows:
	(in thousands)	Non-Controlling Interest
	Balance at December 31, 2013	$	337
	Net loss attributable to Silver Creek		(350	)
	Balance at June 30, 2014	$	(13	)
		Non-Controlling Interest
	Balance at December 31, 2012	$	97
	Net loss attributable to Silver Creek		(339	)
	Balance at June 30, 2013	$	(242	)
Schedule of Available-for-Sale Securities, All of Which Have Maturities of Twelve Months or Less	'
	Available-for-sale securities, all of which have maturities of twelve months or less, as of June 30, 2014 consisted of the following:
		Amortized			Unrealized		Unrealized			Fair
		Cost			Gains		Losses			Value
		(in thousands)
	June 30, 2014:
	Commercial paper	$	14,998		$	—	$	(3	)	$	14,995

Net_Loss_Per_Common_Share_Tabl

Net Loss Per Common Share (Tables)	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted Average Shares	'
	The potential dilutive effect of these securities is shown in the chart below:
		As of June 30,
	(in thousands)	2014		2013
	Options to purchase common stock		21,245		20,447
	Common stock warrants		2,407		2,777
	Conversion premium on the Notes		25,000		—

License_and_Collaboration_Agre1

License and Collaboration Agreements (Tables)	6 Months Ended
	Jun. 30, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Schedule of Revenue Recognized and Assets and Liabilities under Collaborative Arrangements	'
	During the three and six months ended June 30, 2014 and 2013, the Company recognized revenue based on the following components of the Sanofi agreement:
		Three months ended				Six months ended
		June 30,				June 30,
	(in thousands)	2014		2013		2014		2013
	Upfront payment	$	13,268	$	1,250	$	14,518	$	2,500
	Milestone payments		5,529		521		6,049		1,042
	Development services		3,040		14,682		13,740		26,272
	Manufacturing services and other		5,978		1,999		6,542		2,740
	Total	$	27,815	$	18,452	$	40,849	$	32,554
	As of June 30, 2014 and December 31, 2013, the Company maintained the following assets and liabilities related to the Sanofi agreement:
	(in thousands)	June 30, 2014		December 31, 2013
	Accounts receivable, billed	$	3,390	$	2,357
	Accounts receivable, unbilled		2,938		3,417
	Deferred revenue		46,283		73,392

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	'
	The following tables show assets and liabilities measured at fair value on a recurring basis as of June 30, 2014 and December 31, 2013 and the input categories associated with those assets and liabilities:
	As of June 30, 2014	Level 1		Level 2		Level 3
	(in thousands)
	Assets:
	Cash equivalents – money market funds	$	67,108	$	—	$	—
	Investments – commercial paper		—		14,995		—
	As of December 31, 2013	Level 1		Level 2		Level 3
	(in thousands)
	Assets:
	Cash equivalents – money market funds	$	47,740	$	—	$	—
	Cash equivalents – corporate debt securities		—		13,998		—
	Investments – commercial paper		—		49,680		—
	Investments – corporate debt securities		—		40,436		—

Accounts_Payable_Accrued_Expen1

Accounts Payable, Accrued Expenses and Other (Tables)	6 Months Ended
	Jun. 30, 2014
Payables And Accruals [Abstract]	'
Schedule of Accounts Payable, Accrued Expenses and Other	'
	Accounts payable, accrued expenses and other as of June 30, 2014 and December 31, 2013 consisted of the following:
	(in thousands)	June 30, 2014		December 31, 2013
	Accounts payable	$	4,320	$	1,889
	Accrued goods and services		19,075		26,031
	Accrued payroll and related benefits		5,207		7,255
	Accrued interest		2,945		2,926
	Accrued dividends payable		25		25
	Deferred tax incentives		636		688
	Total accounts payable, accrued expenses and other	$	32,208	$	38,814

Borrowings_Tables

Borrowings (Tables)	6 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Schedule of Future Minimum Payments under the Loans Payable	'
	Future minimum payments under indebtedness agreements outstanding as of June 30, 2014 are as follows:
	As of June 30, 2014:	4.50% Convertible			Loan
	(in thousands)	Senior Notes			Agreement
	Remainder of 2014	$	2,813		$	5,626
	2015		5,625			18,135
	2016		5,625			23,804
	2017		5,625			—
	2018 and thereafter		141,875			—
		$	161,563		$	47,565
	Less interest		(36,563	)		(6,365	)
	Less unamortized discount		(48,413	)		(1,862	)
	Less current portion		—			(10,790	)
	Loans payable, net of current portion	$	76,587		$	28,548

Common_Stock_Tables

Common Stock (Tables)	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Schedule of Shares Reserved for Future Issuance	'
	The shares reserved for future issuance as of June 30, 2014 and December 31, 2013 consisted of the following:
	(in thousands)	June 30, 2014		December 31, 2013
	Options to purchase common stock		21,245		20,107
	Common stock warrants		2,407		2,777
	Conversion premium on the Notes		25,000		25,000

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Schedule of Assumptions Used to Calculate Fair Value of Options Granted to Employees and Directors	'
	The assumptions used to estimate the fair value of options granted to employees and directors at the date of grant for the three and six months ended June 30, 2014 were as follows:
		Three months ended June 30,			Six months ended June 30,
		2014		2013	2014		2013
	Risk-free interest rate	1.6-1.9%		0.1-1.4%	1.6-1.9%		0.1-1.4%
	Expected dividend yield	0%		0%	0%		0%
	Expected term	5.0-5.9 years		5.3-5.9 years	5.0-5.9 years		5.3-5.9 years
	Expected volatility	64-70%		67-68%	64-70%		67-68%
Schedule of Recognized Stock-Based Compensation Expense	'
	The Company recognized stock-based compensation expense as follows for the three and six months ended June 30, 2014 and 2013:
		Three months ended June 30,						Six months ended June 30,
	(in thousands)	2014			2013			2014		2013
	Employee awards:
	Research and development	$	1,841		$	1,651		$	3,522	$	2,935
	General and administrative		2,161			1,307			3,453		2,397
	Stock-based compensation for employee awards		4,002			2,958			6,975		5,332
	Stock-based compensation for non-employee awards		153			72			116		84
	Total stock-based compensation	$	4,155		$	3,030		$	7,091	$	5,416
Summary of Stock Option Activity	'
	The following table summarizes stock option activity during the six months ended June 30, 2014:
	(in thousands, except per share amounts and years)	Number			Weighted			Weighted		Aggregate
		of			Average			Average		Intrinsic
		Shares			Exercise Price			Remaining		Value
								Contractual
								Term
	Outstanding, December 31, 2013		20,107		$	3.93			6.11	$	38,348
	Granted		3,107		$	5.17
	Exercised		(1,653	)	$	2.34
	Forfeited		(316	)	$	6.27
	Outstanding, June 30, 2014		21,245		$	4.2			6.29	$	66,353
	Vested and expected to vest, June 30, 2014		20,889		$	4.17			6.24	$	65,734
	Exercisable, June 30, 2014		15,759		$	3.62			5.35	$	58,220

Nature_of_the_Business_Additio

Nature of the Business - Additional Information (Detail) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
	Candidate
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Number of novel therapeutic oncology candidates	6
Unrestricted cash and cash equivalents and available-for-sale securities	$92.70
Agreement termination scheduled date	17-Dec-14

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended				1 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013	31-May-14	Jun. 30, 2014	Jun. 30, 2014
	Security		Security		Silver Creek [Member]	Silver Creek [Member]	Life Sciences Tax Incentive Program 2014 [Member]	Minimum [Member]	Maximum [Member]
							Employees
Summary Of Significant Accounting Policies [Line Items]	'	'	'	'	'	'	'	'	'
Ownership interest percentage	'	'	'	'	64.00%	64.00%	'	'	'
Expected average maturities period of marketable securities classified as available-for-sale	'	'	'	'	'	'	'	'3 months	'12 months
Realized gains (losses) recognized on the sale or maturity of securities	$0	$0	$0	$0	'	'	'	'	'
Aggregate fair value	15,000,000	'	15,000,000	'	'	'	'	'	'
Number of securities in unrealized loss position for less than 12 months	3	'	3	'	'	'	'	'	'
Other-than-temporary-impairment investments	'	'	0	'	'	'	'	'	'
Tax incentives awarded	'	'	'	'	'	'	600,000	'	'
State research and development tax credits monetized	'	'	'	'	'	'	$600,000	'	'
Number of incremental employees pledged to be hired	'	'	'	'	'	'	31	'	'
Performance period	'	'	'	'	'	'	'5 years	'	'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Schedule of Non-Controlling Interest in Subsidiary (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Temporary Equity Disclosure [Abstract]	'	'	'	'
Balance at the beginning of the period	'	'	$337	$97
Net loss attributable to Silver Creek	-181	-169	-350	-339
Balance at the end of the period	($13)	($242)	($13)	($242)

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Schedule of Available-for-Sale Securities, All of Which Have Maturities of Twelve Months or Less (Detail) (Commercial Paper [Member], USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Commercial Paper [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Amortized Cost	$14,998
Unrealized Gains	'
Unrealized Losses	-3
Fair Value	$14,995

Net_Loss_Per_Common_Share_Addi

Net Loss Per Common Share - Additional Information (Detail) (4.50% Convertible Senior Notes [Member], USD $)	1 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2013	Jun. 30, 2014
4.50% Convertible Senior Notes [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Aggregate principal amount	$125	'
Interest rate (as a percent)	4.50%	4.50%

Net_Loss_Per_Common_Share_Sche

Net Loss Per Common Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted Average Shares (Detail)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Options to Purchase Common Stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Potentially dilutive securities (in shares)	21,245	20,447
Common Stock Warrants [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Potentially dilutive securities (in shares)	2,407	2,777
4.50% Convertible Senior Notes [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Potentially dilutive securities (in shares)	25,000	'

License_and_Collaboration_Agre2

License and Collaboration Agreements - Additional Information (Detail) (USD $)

3 Months Ended

6 Months Ended

0 Months Ended

6 Months Ended

0 Months Ended

3 Months Ended

6 Months Ended

0 Months Ended

3 Months Ended

6 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Nov. 10, 2009

Jun. 30, 2014

Jun. 30, 2014

5-May-11

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

5-May-11

5-May-11

Mar. 31, 2012

Jun. 30, 2014

Dec. 31, 2013

Sanofi [Member]

Sanofi [Member]

Sanofi [Member]

PharmaEngine [Member]

PharmaEngine [Member]

PharmaEngine [Member]

PharmaEngine [Member]

PharmaEngine [Member]

PharmaEngine [Member]

PharmaEngine [Member]

PharmaEngine [Member]

Actavis [Member]

Actavis [Member]

License and Collaboration Agreements [Member]

License and Collaboration Agreements [Member]

License and Collaboration Agreements [Member]

License and Collaboration Agreements [Member]

License and Collaboration Agreements [Member]

Development and Regulatory Milestone [Member]

Sales Milestone [Member]

Phase 3 Clinical Trial in Pancreatic Cancer [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Upfront license fee received

'

'

'

'

$60,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Milestone license fee received

'

'

'

'

'

25,000,000

'

'

'

'

'

'

'

'

'

2,700,000

'

Agreement termination scheduled date

'

'

17-Dec-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected development period from the effective date of agreement

'

'

'

'

'12 years

'

'

'

'

'

'

'

'

'

'

'

'

Development services performed

'

'

'

'

'

'

5,800,000

'

'

'

'

'

'

'

'

'

'

Upfront license fees paid

'

'

'

'

'

'

'

10,000,000

'

'

'

'

'

'

'

'

'

Maximum milestone payment obligation

'

'

'

'

'

'

'

'

'

'

'

'

80,000,000

130,000,000

'

'

'

Milestone payment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,000,000

'

'

Research and development expenses

33,795,000

42,465,000

64,119,000

79,454,000

'

'

'

'

100,000

200,000

200,000

500,000

'

'

'

'

'

Eligible milestone payments

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

15,500,000

'

Agreement expiration term respect to each product

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 years

'

Additional renewal term

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'2 years

'

Notice period of termination

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'90 days

'

Milestones and development expenses

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$3,000,000

$2,100,000

License_and_Collaboration_Agre3

License and Collaboration Agreements - Schedule of Revenue Recognized and Assets and Liabilities under Collaborative Arrangements (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'	'	'
Total	$27,815	$18,452	$40,849	$33,107	'
License and Collaboration Agreements [Member] | Sanofi [Member]	'	'	'	'	'
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'	'	'
Upfront payment	13,268	1,250	14,518	2,500	'
Milestone payments	5,529	521	6,049	1,042	'
Development services	3,040	14,682	13,740	26,272	'
Manufacturing services and other	5,978	1,999	6,542	2,740	'
Total	27,815	18,452	40,849	32,554	'
Accounts receivable, billed	3,390	'	3,390	'	2,357
Accounts receivable, unbilled	2,938	'	2,938	'	3,417
Deferred revenue	$46,283	'	$46,283	'	$73,392

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (Recurring Basis [Member], USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Level 1 [Member] | Money Market Funds [Member]	'	'
Assets:	'	'
Cash equivalents	$67,108	$47,740
Level 2 [Member] | Commercial Paper [Member]	'	'
Assets:	'	'
Investments	14,995	49,680
Level 2 [Member] | Corporate Debt Securities [Member]	'	'
Assets:	'	'
Cash equivalents	'	13,998
Investments	'	$40,436

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Marketable securities with an original maturity	'Greater than three months
Fair Value [Member] | Level 3 [Member] | Hercules [Member]	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Notes	39.6
Carrying Value [Member] | Level 3 [Member] | Hercules [Member]	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Notes	40.5
Senior Convertible Notes [Member]	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Principal amount	125
Senior Convertible Notes [Member] | Fair Value [Member] | Level 2 [Member]	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Notes	170.2
Senior Convertible Notes [Member] | Carrying Value [Member] | Level 2 [Member]	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Notes	76.6
Maximum [Member]	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'
Liquid investments with an original maturity	'3 months

Accounts_Payable_Accrued_Expen2

Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property Plant And Equipment Useful Life And Values [Abstract]	'	'
Accounts payable	$4,320	$1,889
Accrued goods and services	19,075	26,031
Accrued payroll and related benefits	5,207	7,255
Accrued interest	2,945	2,926
Accrued dividends payable	25	25
Deferred tax incentives	636	688
Total accounts payable, accrued expenses and other	$32,208	$38,814

Borrowings_Schedule_of_Future_

Borrowings - Schedule of Future Minimum Payments under the Loans Payable (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt Instrument [Line Items]	'	'
Loans payable, net of current portion	$105,135	$103,427
4.50% Convertible Senior Notes [Member]	'	'
Debt Instrument [Line Items]	'	'
Remainder of 2014	2,813	'
2015	5,625	'
2016	5,625	'
2017	5,625	'
2018 and thereafter	141,875	'
Loans payable, gross	161,563	'
Less interest	-36,563	'
Less unamortized discount	-48,413	'
Loans payable, net of current portion	76,587	'
Loans Payable [Member] | Loan and Security Agreement [Member]	'	'
Debt Instrument [Line Items]	'	'
Remainder of 2014	5,626	'
2015	18,135	'
2016	23,804	'
Loans payable, gross	47,565	'
Less interest	-6,365	'
Less unamortized discount	-1,862	'
Less current portion	-10,790	'
Loans payable, net of current portion	$28,548	'

Borrowings_Additional_Informat

Borrowings - Additional Information (Detail) (USD $)

0 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

0 Months Ended

1 Months Ended

3 Months Ended

6 Months Ended

Jun. 25, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Dec. 31, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Nov. 30, 2012

Jul. 31, 2013

Jul. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Hercules [Member]

Silver Creek Convertible Note [Member]

Silver Creek Convertible Note [Member]

Silver Creek Convertible Note [Member]

Silver Creek Convertible Note [Member]

Scenario, Forecast [Member]

Loan and Security Agreement [Member]

Loan and Security Agreement [Member]

Loan and Security Agreement [Member]

Loan and Security Agreement [Member]

Loan and Security Agreement [Member]

4.50% Convertible Senior Notes [Member]

4.50% Convertible Senior Notes [Member]

4.50% Convertible Senior Notes [Member]

4.50% Convertible Senior Notes [Member]

Silver Creek [Member]

Minimum [Member]

Silver Creek Convertible Note [Member]

Hercules [Member]

Silver Creek [Member]

Silver Creek [Member]

Schedule Of Debt Instruments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate principal amount

'

'

'

'

'

'

'

'

$300,000

'

'

'

'

'

'

'

'

$125,000,000

'

'

Proceeds from issuance of convertible senior notes, net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

120,600,000

'

'

Interest rate (as a percent)

'

'

'

'

'

'

'

'

'

'

6.00%

'

'

'

'

'

4.50%

4.50%

4.50%

4.50%

Debt Maturity Date

'

'

'

15-Jul-20

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Conversion rate of common stock shares per $1,000 principal amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

160

'

'

'

Conversion ratio, principal amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000

1,000

'

'

Initial conversion price of shares (in dollars per share)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$6.25

$6.25

'

'

Underwriting discounts and commissions and offering expenses

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,400,000

'

'

'

Interest expense

'

4,570,000

1,293,000

9,081,000

2,513,000

'

'

'

'

'

'

1,200,000

1,200,000

2,400,000

2,400,000

'

'

'

3,400,000

6,800,000

Aggregate principal amount of loans received

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

40,000,000

'

'

'

'

Extension period for interest-only payment

'4 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amortization schedule of loan agreement

'

'

'

'30 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Beginning date for equal monthly installments of loan agreement

'

'

'

1-Oct-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Discount on loan recorded as a non-current liability to be paid upon full repayment or maturity of the loans

'

'

'

'

'

'

'

'

'

'

'

1,200,000

'

1,200,000

'

'

'

'

'

'

Less unamortized discount

'

'

'

'

'

1,600,000

'

'

'

'

'

'

'

'

'

'

'

'

48,413,000

48,413,000

Amount of gross proceeds from qualifying equity financing in which holders would automatically convert into the next qualifying equity financing at a 25% discount

'

'

'

'

'

'

'

'

'

4,000,000

'

'

'

'

'

'

'

'

'

'

Discount on automatic conversion into the next qualifying equity financing (as a percent)

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

Outstanding borrowings net

'

'

'

'

'

'

300,000

300,000

'

'

'

'

'

'

'

'

'

'

'

'

Interest expense

'

'

'

'

'

'

$0

$0

'

'

'

'

'

'

'

'

'

'

'

'

Common_Stock_Additional_Inform

Common Stock - Additional Information (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Feb. 28, 2014
In Millions, except Share data, unless otherwise specified			Hercules [Member]
Class of Stock [Line Items]	'	'	'
Common stock, shares authorized	200,000,000	200,000,000	'
Common stock, par value	$0.01	$0.01	'
Common stock, shares issued	104,513,000	102,523,000	'
Common stock, shares outstanding	104,513,000	102,523,000	'
Warrants exercised to purchase common stock	'	'	302,143
Proceeds from exercise of warrant	'	'	$1.10

Common_Stock_Schedule_of_Share

Common Stock - Schedule of Shares Reserved for Future Issuance (Detail)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Equity [Abstract]	'	'
Options to purchase common stock	21,245	20,107
Common stock warrants	2,407	2,777
Conversion premium on the Notes	25,000	25,000

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail)	6 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jan. 31, 2014	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
		Director [Member]	Director [Member]	Director [Member]	Director [Member]	Employee [Member]	Stock Incentive Plan 2011 [Member]	Stock Incentive Plan 2011 [Member]	Stock Incentive Plan 2011 [Member]	Stock Incentive Plan 2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'	'
Shares of common stock available for grant	'	'	'	'	'	'	'	2,500,000	'	1,700,000
Additional common stock available for grant (in shares)	'	'	'	'	'	'	3,600,000	'	'	'
Stock options issued (in shares)	3,107,000	'	'	'	'	'	'	3,100,000	3,000,000	'
Options vesting period	'	'1 year	'1 year	'1 year	'1 year	'3 years	'	'	'	'

StockBased_Compensation_Schedu

Stock-Based Compensation - Schedule of Assumptions Used to Calculate Fair Value of Options Granted to Employees and Directors (Detail) (Options to Purchase Common Stock [Member])	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Risk-free interest rate	1.60%	0.10%	1.60%	0.10%
Expected term	'5 years	'5 years 3 months 18 days	'5 years	'5 years 3 months 18 days
Expected volatility	64.00%	67.00%	64.00%	67.00%
Maximum [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Risk-free interest rate	1.90%	1.40%	1.90%	1.40%
Expected term	'5 years 10 months 24 days	'5 years 10 months 24 days	'5 years 10 months 24 days	'5 years 10 months 24 days
Expected volatility	70.00%	68.00%	70.00%	68.00%

StockBased_Compensation_Schedu1

Stock-Based Compensation - Schedule of Recognized Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense for employee awards	$4,002	$2,958	$6,975	$5,332
Stock-based compensation expense for non-employee awards	153	72	116	84
Total stock-based compensation	4,155	3,030	7,091	5,416
Research and Development Expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense for employee awards	1,841	1,651	3,522	2,935
General and Administrative Expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense for employee awards	$2,161	$1,307	$3,453	$2,397

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $)	6 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding [Roll Forward]	'	'
Number of Shares, Outstanding, Beginning balance	20,107	'
Number of Shares, Granted	3,107	'
Number of Shares, Exercised	-1,653	'
Number of Shares, Forfeited	-316	'
Number of Shares, Outstanding, Ending balance	21,245	20,107
Number of shares vested and expected to vest	20,889	'
Number of stock option exercisable	15,759	'
Weighted Average Exercise Price, Outstanding, Beginning balance	$3.93	'
Weighted Average Exercise Price, Granted	$5.17	'
Weighted Average Exercise Price, Exercised	$2.34	'
Weighted Average Exercise Price, Forfeited	$6.27	'
Weighted Average Exercise Price, Outstanding, Ending balance	$4.20	$3.93
Weighted average exercise price of shares vested and expected to vest (in dollars per share)	$4.17	'
Weighted average exercise price for exercisable option (in dollars per share)	$3.62	'
Weighted Average Remaining Contractual Term	'6 years 3 months 15 days	'6 years 1 month 10 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	'6 years 2 months 27 days	'
Weighted Average Remaining Contractual Term, Exercisable	'5 years 4 months 6 days	'
Aggregate Intrinsic Value, Outstanding, Beginning balance	$38,348	'
Aggregate Intrinsic Value, Outstanding, Ending balance	66,353	38,348
Aggregate Intrinsic Value, Vested and expected to vest	65,734	'
Aggregate Intrinsic Value, Exercisable	$58,220	'

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Commitments And Contingencies Disclosure [Abstract]	'	'	'	'
Total rent expense	$1.50	$1.40	$3	$2.60