BioCryst Pharmaceuticals (BCRX) 10-Q 9 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Entity Registrant Name	'BIOCRYST PHARMACEUTICALS INC	'
Entity Central Index Key	'0000882796	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	60,064,634

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets	'	'
Cash and cash equivalents	$13,584	$21,164
Restricted cash	150	151
Investments	17,807	16,891
Receivables	3,280	2,115
Prepaid expenses and other current assets	835	1,725
Deferred collaboration expense	75	75
Total current assets	35,731	42,121
Investments	2,679	2,582
Furniture and equipment, net	260	306
Deferred collaboration expense	222	237
Other assets	4,495	3,620
Total assets	43,387	48,866
Liabilities and Stockholders' Equity	'	'
Accounts payable	1,352	4,174
Accrued expenses	6,312	5,742
Interest payable	4,552	3,867
Deferred collaboration revenue	1,473	1,473
Total current liabilities	13,689	15,256
Deferred collaboration revenue	4,440	4,736
Foreign currency derivative	981	'
Non-recourse notes payable	30,000	30,000
Stockholders' equity:	'	'
Preferred stock, $0.001 par value; shares authorized - 5,000; no shares issued and outstanding	'	'
Common stock, $0.01 par value: shares authorized - 95,000; shares issued and outstanding - 60,065 in 2014 and 59,092 in 2013	601	591
Additional paid-in capital	426,520	420,988
Accumulated other comprehensive income	2	4
Accumulated deficit	-432,846	-422,709
Total stockholders' deficit	-5,723	-1,126
Total liabilities and stockholders' equity	$43,387	$48,866

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	'	'
Preferred stock, shares outstanding	'	'
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	95,000	95,000
Common stock, shares issued	60,065	59,092
Common stock, shares outstanding	60,065	59,092

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Revenues	'	'
Royalty revenue	$1,821	$1,924
Collaborative and other research and development	1,637	1,630
Total revenues	3,458	3,554
Expenses	'	'
Research and development	9,183	7,215
General and administrative	1,588	1,578
Royalty	73	77
Total operating expenses	10,844	8,870
Loss from operations	-7,386	-5,316
Interest and other income	17	33
Interest expense	-1,242	-1,180
(Loss) gain on foreign currency derivative	-1,526	1,957
Net loss	-10,137	-4,506
Basic and diluted net loss per common share	($0.17)	($0.09)
Weighted average shares outstanding	59,589	51,073
Unrealized loss on available for sale investments	-2	-12
Comprehensive loss	($10,139)	($4,518)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Operating activities	'	'
Net loss	($10,137)	($4,506)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'
Depreciation and amortization	53	97
Stock-based compensation expense	1,610	1,602
Amortization of debt issuance costs	110	110
Change in fair value of foreign currency derivative	1,526	-1,958
Changes in operating assets and liabilities:	'	'
Receivables	-1,165	237
Prepaid expenses and other assets	892	-679
Deferred collaboration expense	15	95
Accounts payable and accrued expenses	-2,252	-7,114
Interest payable	685	1,070
Deferred collaboration revenue	-296	-152
Net cash used in operating activities	-8,959	-11,198
Investing activities	'	'
Acquisitions of furniture and equipment	-7	'
Change in restricted cash	1	-308
Purchases of investments	-9,367	'
Sales and maturities of investments	8,350	2,380
Net cash (used in) provided by investing activities	-1,023	2,072
Financing activities	'	'
Sale of common stock, net	'	360
Exercise of stock options	3,804	102
Employee stock purchase plan sales	128	68
(Payment) receipt of foreign currency derivative collateral	-1,530	2,510
Net cash provided by financing activities	2,402	3,040
Decrease in cash and cash equivalents	-7,580	-6,086
Cash and cash equivalents at beginning of period	21,164	20,891
Cash and cash equivalents at end of period	$13,584	$14,805

Significant_Accounting_Policie

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Significant Accounting Policies	'
	Note 1 — Significant Accounting Policies
	The Company
	BioCryst Pharmaceuticals, Inc. (the “Company”) is a biotechnology company that designs, optimizes and develops novel drugs that block key enzymes involved in the pathogenesis of diseases. The Company focuses on rare and infectious diseases in which unmet medical needs exist and that are aligned with its capabilities and expertise. The Company was incorporated in Delaware in 1986 and its headquarters is located in Durham, North Carolina. The Company integrates the disciplines of biology, crystallography, medicinal chemistry and computer modeling to discover and develop small molecule pharmaceuticals through the process known as structure-guided drug design. BioCryst has incurred losses and negative cash flows from operations since inception.
	Based on its current operating plans, the Company expects it has sufficient liquidity, with its existing cash and investments of $34,220, to continue its planned operations into the first quarter of 2015. The Company’s liquidity needs, and ability to address those needs, will largely be determined by the success of its product candidates and key development and regulatory events in the future. In order to continue its operations substantially beyond the first quarter of 2015 it will need to: (1) successfully secure or increase U.S. Government funding of its programs; (2) out-license rights to certain of its product candidates, pursuant to which the Company would receive cash milestones; (3) raise additional capital through equity or debt financings or from other sources; (4) obtain product candidate regulatory approvals, which would generate revenue and cash flow; (5) reduce spending on one or more research and development programs; and/or (6) restructure operations. The Company will continue to incur operating losses and negative cash flows until revenues reach a level sufficient to support ongoing operations.
	Basis of Presentation
	Beginning in March 2011, the consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, JPR Royalty Sub LLC (“Royalty Sub”). Royalty Sub was formed in connection with a $30,000 financing transaction the Company completed on March 9, 2011. See Note 4, Royalty Monetization, for a further description of this transaction. All intercompany transactions and balances have been eliminated.
	The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial reporting and the instructions to Form 10-Q and do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. Such financial statements reflect all adjustments that are, in management’s opinion, necessary to present fairly, in all material respects, the Company’s consolidated financial position, results of operations, and cash flows. There were no adjustments other than normal recurring adjustments.
	These financial statements should be read in conjunction with the financial statements for the year ended December 31, 2013 and the notes thereto included in the Company’s 2013 Annual Report on Form 10-K. Interim operating results are not necessarily indicative of operating results for the full year. The balance sheet as of December 31, 2013 has been derived from the audited consolidated financial statements included in the Company’s most recent Annual Report on Form 10-K.
	Reclassifications
	In the first quarter of 2014, the Company changed its classification of patent costs. This change resulted in $196 of patent expenses being reclassified from research and development expense to general and administrative expense for the three months ended March 31, 2013. This reclassification had no effect on previously reported total operating expenses or net loss amounts.
	Cash and Cash Equivalents
	The Company generally considers cash equivalents to be all cash held in commercial checking accounts, money market accounts or investments in debt instruments with maturities of three months or less at the time of purchase. The carrying value of cash and cash equivalents approximates fair value due to the short-term nature of these items.
	Restricted Cash
	Restricted cash as of March 31, 2014 reflects $150 the Company is required to maintain in an interest bearing certificate of deposit to serve as collateral for a corporate credit card program.
	Investments
	The Company invests in high credit quality investments in accordance with its investment policy, which is designed to minimize the possibility of loss. The objective of the Company’s investment policy is to ensure the safety and preservation of invested funds, as well as maintaining liquidity sufficient to meet cash flow requirements. The Company places its excess cash with high credit quality financial institutions, commercial companies, and government agencies in order to limit the amount of its credit exposure. Per its policy, the Company is able to invest in marketable debt securities that may consist of U.S. Government and government agency securities, money market and mutual fund investments, municipal and corporate notes and bonds, commercial paper and asset or mortgage-backed securities, among others. The Company’s investment policy requires it to purchase high-quality marketable securities with a maximum individual maturity of three years and requires an average portfolio maturity of no more than 18 months. Some of the securities the Company invests in may have market risk. This means that a change in prevailing interest rates may cause the principal amount of the investment to fluctuate. To minimize this risk, the Company schedules its investments with maturities that coincide with expected cash flow needs, thus avoiding the need to redeem an investment prior to its maturity date. Accordingly, the Company does not believe it has a material exposure to interest rate risk arising from its investments. Generally, the Company’s investments are not collateralized. The Company has not realized any significant losses from its investments.
	The Company classifies all of its investments as available-for-sale. Unrealized gains and losses on investments are recognized in comprehensive income/(loss), unless an unrealized loss is considered to be other than temporary, in which case the unrealized loss is charged to operations. The Company periodically reviews its investments for other than temporary declines in fair value below cost basis and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The Company believes the individual unrealized losses represent temporary declines primarily resulting from interest rate changes. Realized gains and losses are reflected in interest and other income in the Consolidated Statements of Comprehensive Loss and are determined using the specific identification method with transactions recorded on a settlement date basis. Investments with original maturities at date of purchase beyond three months and which mature at or less than 12 months from the balance sheet date are classified as current. Investments with a maturity beyond 12 months from the balance sheet date are classified as long-term. At March 31, 2014, the Company believes that the costs of its investments are recoverable in all material respects.
	The following tables summarize the fair value of the Company’s investments by type. The estimated fair value of the Company’s fixed income investments are classified as Level 2 in the fair value hierarchy as defined in U.S. GAAP. These fair values are obtained from independent pricing services which utilize Level 2 inputs.
			March 31, 2014
			Amortized		Accrued		Gross		Gross		Estimated
			Cost		Interest		Unrealized		Unrealized		Fair Value
							Gains		Losses
	Obligations of U.S. Government and its agencies		$	4,800	$	1	$	—	$	1	$	4,800
	Corporate debt securities			6,045		46		2		1		6,092
	Commercial paper			9,592		—		2		—		9,594
	Total investments		$	20,437	$	47	$	4	$	2	$	20,486
			December 31, 2013
			Amortized		Accrued		Gross		Gross		Estimated
			Cost		Interest		Unrealized		Unrealized		Fair Value
							Gains		Losses
	Obligations of U.S. Government and its agencies		$	4,899	$	1	$	1	$	—	$	4,901
	Corporate debt securities			8,528		47		2		1		8,576
	Commercial paper			5,994		—		2		—		5,996
	Total investments		$	19,421	$	48	$	5	$	1	$	19,473
	The following table summarizes the scheduled maturity for the Company’s investments at March 31, 2014 and December 13, 2013.
			2014		2013
	Maturing in one year or less		$	17,807	$	16,891
	Maturing after one year through two years			2,679		2,582
	Total investments		$	20,486	$	19,473
	Receivables
	Receivables are recorded for amounts due to the Company related to reimbursable research and development costs from the U.S. Department of Health and Human Services or royalty receivables from Shionogi & Co. Ltd. At March 31, 2014 and December 31, 2013, the Company had the following receivables.
			March 31, 2014
			Billed		Unbilled		Total
	U.S. Department of Health and Human Services		$	195	$	1,270	$	1,465
	Shionogi & Co. Ltd.			1,815		—		1,815
	Total receivables		$	2,010	$	1,270	$	3,280
			December 31, 2013
			Billed		Unbilled		Total
	U.S. Department of Health and Human Services		$	90	$	1,573	$	1,663
	Shionogi & Co. Ltd.			452		—		452
	Total receivables		$	542	$	1,573	$	2,115
	Monthly invoices are submitted to the U.S. Department of Health and Human Services related to reimbursable research and development costs. The Company is also entitled to monthly reimbursement of indirect costs based on rates stipulated in the underlying contract. The Company’s calculations of its indirect cost rates are subject to audit by the federal government.
	Patents and Licenses
	The Company seeks patent protection on internally developed processes and products. All patent related costs are expensed to general and administrative expenses when incurred as recoverability of such expenditures is uncertain.
	Accrued Expenses
	The Company generally enters into contractual agreements with third-party vendors who provide research and development, manufacturing, and other services in the ordinary course of business. Some of these contracts are subject to milestone-based invoicing and services are completed over an extended period of time. The Company records liabilities under these contractual commitments when it determines an obligation has been incurred, regardless of the timing of the invoice. This process involves reviewing open contracts and purchase orders, communicating with applicable Company personnel to identify services that have been performed on its behalf and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of actual cost. The majority of service providers invoice the Company monthly in arrears for services performed. The Company makes estimates of accrued expenses as of each balance sheet date in its financial statements based on the facts and circumstances. The Company periodically confirms the accuracy of its estimates with the service providers and makes adjustments if necessary. Examples of estimated accrued expenses include:
		•		fees paid to Clinical Research Organizations (“CROs”) in connection with preclinical and toxicology studies and clinical trials;
		•		fees paid to investigative sites in connection with clinical trials;
		•		fees paid to contract manufacturers in connection with the production of our raw materials, drug substance and drug products; and
		•		professional fees.
	The Company bases its expenses related to clinical trials on its estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and clinical research organizations that conduct and manage clinical trials on the Company’s behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Accrued expenses as of March 31, 2014 and December 31, 2013 included $2,076 and $2,210, respectively, of research and development costs.
	Income Taxes
	The liability method is used in the Company’s accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse.
Accumulated Other Comprehensive (Loss) Income
Accumulated other comprehensive (loss) income is comprised of unrealized gains and losses on investments available-for-sale and is disclosed as a separate component of stockholders’ equity. No reclassifications out of accumulated other comprehensive (loss) income were recorded during the three months ended March 31, 2014 and 2013.
Revenue Recognition
The Company recognizes revenues from collaborative and other research and development arrangements and product sales. Revenue is realized or realizable and earned when all of the following criteria are met: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the seller’s price to the buyer is fixed or determinable; and (iv) collectability is reasonably assured.
Collaborative and Other Research and Development Arrangements and Royalties
Revenue from license fees, royalty payments, event payments, and research and development fees are recognized as revenue when the earnings process is complete and the Company has no further continuing performance obligations or the Company has completed the performance obligations under the terms of the agreement. Fees received under licensing agreements that are related to future performance are deferred and recognized over an estimated period determined by management based on the terms of the agreement and the products licensed. In the event a license agreement contains multiple deliverables, the Company evaluates whether the deliverables are separate or combined units of accounting. Revisions to revenue or profit estimates as a result of changes in the estimated revenue period are recognized prospectively.
Under certain of our license agreements, the Company receives royalty payments based upon our licensees’ net sales of covered products. The Company recognizes royalty revenues when it can reliably estimate such amounts and collectability is reasonably assured.
Reimbursements received for direct out-of-pocket expenses related to research and development costs are recorded as revenue in the Consolidated Statements of Comprehensive Loss rather than as a reduction in expenses. Event payments are recognized as revenue upon the achievement of specified events if (1) the event is substantive in nature and the achievement of the event was not reasonably assured at the inception of the agreement and (2) the fees are non-refundable and non-creditable. Any event payments received prior to satisfying these criteria are recorded as deferred revenue. Under the Company’s contracts with the U.S. Department of Health and Human Services, (“BARDA/HHS”), and the National Institute of Allergy and Infectious Diseases (“NIAID/HHS”), revenue is recognized as reimbursable direct and indirect costs are incurred.
Product Sales
Sales are recognized when there is persuasive evidence that an arrangement exists, title has passed, the price was fixed and determinable, and collectability is reasonably assured. Product sales are recognized net of estimated allowances, discounts, sales returns, chargebacks and rebates.
The Company recorded the following revenues for the three months ended March 31, 2014 and 2013:
		2014		2013
Royalty revenue		$	1,821	$	1,924
Collaborative and other research and development revenues:
U.S. Department of Health and Human Services			1,341		1,334
Shionogi (Japan)			296		296
Total revenues		$	3,458	$	3,554
Research and Development Expenses
The Company’s research and development costs are charged to expense when incurred. Research and development expenses include all direct and indirect development costs related to the development of the Company’s portfolio of product candidates. Advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are recognized as expense when the related goods are delivered or the related services are performed. Research and development expenses include, among other items, personnel costs, including salaries and benefits, manufacturing costs, clinical, regulatory, and toxicology services performed by CROs, materials and supplies, and overhead allocations consisting of various administrative and facilities related costs. Most of the Company’s manufacturing and clinical and preclinical studies are performed by third-party CROs. Costs for studies performed by CROs are accrued by the Company over the service periods specified in the contracts and estimates are adjusted, if required, based upon the Company’s on-going review of the level of services actually performed.
Additionally, the Company has license agreements with third parties, such as Albert Einstein College of Medicine of Yeshiva University (“AECOM”), Industrial Research, Ltd. (“IRL”), and the University of Alabama at Birmingham (“UAB”), which require fees related to sublicense agreements or maintenance fees. The Company expenses sublicense payments as incurred unless they are related to revenues that have been deferred, in which case the expenses are deferred and recognized over the related revenue recognition period. The Company expenses maintenance payments as incurred.
Deferred collaboration expenses represent sub-license payments, paid to the Company’s academic partners upon receipt of consideration from various commercial partners, and other consideration paid to our academic partners for modification to existing license agreements. These deferred expenses would not have been incurred without receipt of such payments or modifications from the Company’s commercial partners and are being expensed in proportion to the related revenue being recognized. The Company believes that this accounting treatment appropriately matches expenses with the associated revenue.
Stock-Based Compensation
All share-based payments, including grants of stock option awards and restricted stock awards, are recognized in the Company’s Consolidated Statements of Comprehensive Loss based on their fair values. The fair value of stock option awards is estimated using the Black-Scholes option pricing model. The fair value of restricted stock awards is based on the grant date closing price of the common stock. Stock-based compensation cost is recognized as expense on a straight-line basis over the requisite service period of the award.
Interest Expense and Deferred Financing Costs
Interest expense for the three months ended March 31, 2014 and 2013 was $1,242 and $1,180, respectively, and relates to the issuance of the PhaRMA Notes (defined in Note 4). Costs directly associated with the issuance of the PhaRMA Notes have been capitalized and are included in other non-current assets on the Consolidated Balance Sheets. These costs are being amortized to interest expense over the term of the PhaRMA Notes using the effective interest rate method. Amortization of deferred financing costs included in interest expense was $110 for each of the three months ended March 31, 2014 and 2013.
Currency Hedge Agreement
In connection with the issuance by Royalty Sub of the PhaRMA Notes, the Company entered into a Currency Hedge Agreement (defined in Note 4) to hedge certain risks associated with changes in the value of the Japanese yen relative to the U.S. dollar. The Currency Hedge Agreement does not qualify for hedge accounting treatment; therefore, mark-to-market adjustments are recognized in the Company’s Consolidated Statements of Comprehensive Loss. Cumulative mark-to-market adjustments for the three months ended March 31, 2014 and 2013 resulted in a loss of $1,526 and a gain of $1,957, respectively. Mark-to-market adjustments are determined by a third party pricing model that uses quoted prices in markets that are not actively traded and for which significant inputs are observable directly or indirectly, representing Level 2 in the fair value hierarchy as defined by U.S. GAAP. The Company is also required to post collateral in connection with the mark-to-market adjustments based on thresholds defined in the Currency Hedge Agreement. As of March 31, 2014, $1,530 of hedge collateral was posted under the agreement. No hedge collateral was posted under the agreement as of December 31, 2013.
Net Loss Per Share
Net loss per share is based upon the weighted average number of common shares outstanding during the period. Diluted loss per share is equivalent to basic net loss per share for all periods presented herein because common equivalent shares from unexercised stock options and common shares expected to be issued under the Company’s employee stock purchase plan were anti-dilutive. The calculation of diluted earnings per share for the three months ended March 31, 2014 and 2013 does not include 5,206 and 681, respectively, of such potential common shares, as their impact would be anti-dilutive.
Use of Estimates
The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements. Actual results could differ from those estimates.
Concentration of Market Risk
The reimbursement of peramivir and BCX4430 development expenses is a significant source of the Company’s revenue and one which has an underlying cash flow stream. This revenue and cash flow is earned under cost-plus-fixed-fee contracts with BARDA/HHS and NIAID/HHS, respectively. The Company relies on BARDA/HHS and NIAID/HHS to reimburse predominantly all of the development costs for its peramivir and BCX4430 programs, respectively. Accordingly, reimbursement of these expenses represents a significant portion of the Company’s collaborative and other research and development revenues. The completion and/or termination of these programs/collaborations could negatively impact the Company’s future Consolidated Statements of Comprehensive Loss and Cash Flows. In addition, the Company also recognizes royalty revenue from the net sales of RAPIACTA®; however, the underlying cash flow from these royalty payments goes directly to pay the interest, and then the principal, on the Company’s non-recourse notes payable. Payment of the interest and the ultimate repayment of principal of these notes will be entirely funded by future royalty payments derived from net sales of RAPIACTA®. At March 31, 2014, there was a significant underpayment of interest on the PhaRMA Notes, which if unpaid at September 1, 2014, will constitute an event of default under the PhaRMA Notes. If an event of default were to occur under the PhaRMA Notes, the holders of the PhaRMA Notes may be able to foreclose on the collateral securing the PhaRMA Notes and our equity interest in Royalty Sub and exercise other remedies available to them under the indenture in respect of the PhaRMA Notes. In such event, we may not realize the benefit of future royalty payments that might otherwise accrue to us following repayment of the PhaRMA Notes and we might otherwise be adversely affected. The Company’s drug development activities are performed by a limited group of third party vendors. If any of these vendors were unable to perform their services, this could significantly impact the Company’s ability to complete its drug development activities.
Credit Risk
Cash equivalents and investments are financial instruments which potentially subject the Company to concentration of risk to the extent recorded on the Consolidated Balance Sheets. The Company deposits excess cash with major financial institutions in the United States. Balances may exceed the amount of insurance provided on such deposits. The Company believes it has established guidelines for investment of its excess cash relative to diversification and maturities that maintain safety and liquidity. To minimize the exposure due to adverse shifts in interest rates, the Company maintains a portfolio of investments with an average maturity of approximately 24 months or less. The majority of the Company’s receivables are due from the U.S. Government, for which there is no assumed credit risk.
Recent Accounting Pronouncements
There have been no recent accounting pronouncements or changes in accounting pronouncements since the recent accounting pronouncements described in the Company’s 2013 Annual Report on Form 10-K that are of significance to the Company.

StockBased_Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation	'
	Note 2 — Stock-Based Compensation
	As of March 31, 2014, the Company had two stock-based employee compensation plans, the Stock Incentive Plan (“Incentive Plan”) and the Employee Stock Purchase Plan (“ESPP”), both which were amended and restated in March 2012 and approved by the Company’s stockholders in May 2012. Stock-based compensation expense of $1,610 ($1,558 of expense related to the Incentive Plan and $52 of expense related to the ESPP) was recognized during the first three months of 2014, while $1,602 ($1,576 of expense related to the Incentive Plan and $26 of expense related to the ESPP) was recognized during the first three months of 2013.
	There was approximately $11,789 of total unrecognized compensation cost related to non-vested stock option awards and restricted stock awards granted by the Company as of March 31, 2014. That cost is expected to be recognized as follows: $3,406 during the remainder of 2014, $3,466 in 2015, $2,607 in 2016, $2,141 in 2017 and $169 in 2018. In addition, the Company has outstanding performance-based stock options for which no compensation expense is recognized until “performance” has occurred and the award vests. At the time of vesting, compensation expense will be recognized.
	Stock Incentive Plan
	The Company grants stock option awards and restricted stock awards to its employees, directors, and consultants under the Incentive Plan. Under the Incentive Plan, stock option awards are granted with an exercise price equal to the market price of the Company’s stock at the date of grant. Prior to March 1, 2011, stock option awards granted to employees generally vest 25% after one year and monthly thereafter on a pro rata basis over the next three years until fully vested after four years. Commencing March 1, 2011, stock option awards granted to employees generally vest 25% each year until fully vested after four years. In January 2013, the Company made retention grants of stock option awards and restricted stock. These awards vest 50% each year until fully vested after two years. In August 2013, the Company issued 1,032 performance-based stock options. These awards vest upon successful completion of specific development milestones. As of March 31, 2014 and based on the information available at that time, it is not considered probable that any of the specific development milestones will be met and, accordingly, no compensation expense has been recognized for options under this performance based grant award. Stock option awards granted to non-employee directors of the Company generally vest monthly over one year. All stock option awards have contractual terms of 5 to 10 years. The vesting exercise provisions of all awards granted under the Incentive Plan are subject to acceleration in the event of certain stockholder-approved transactions, or upon the occurrence of a change in control as defined in the Incentive Plan.
	Related activity under the Incentive Plan is as follows:
		Awards			Options			Weighted
		Available			Outstanding			Average
								Exercise
								Price
	Balance December 31, 2013		1,082			8,986		$	4.99
	Restricted stock awards granted		(593	)		—			—
	Restricted stock awards cancelled		—			—			—
	Stock option awards granted		(391	)		391			10.79
	Stock option awards exercised		—			(832	)		5.18
	Stock option awards cancelled		—			—			—
	Balance March 31, 2014		98			8,545		$	5.24
	For stock option awards granted under the Incentive Plan during the first three months of 2014 and 2013, the fair value was estimated on the date of grant using a Black-Scholes option pricing model and the assumptions noted in the table below. The weighted average grant date fair value per share of the awards granted during the first three months of 2014 and 2013 was $8.28 and $0.88, respectively. The fair value of the stock option awards is amortized to expense over the vesting periods using a straight-line expense attribution method. The following table summarizes the key assumptions used by the Company to value the stock option awards granted during the first three months of 2014 and 2013. The expected life is based on the average of the assumption that all outstanding stock option awards will be exercised at full vesting and the assumption that all outstanding stock option awards will be exercised at the midpoint of the current date (if already vested) or at full vesting (if not yet vested) and the full contractual term. The expected volatility represents the historical volatility on the Company’s publicly traded common stock. The Company has assumed no expected dividend yield, as dividends have never been paid to stock or option holders and will not be paid for the foreseeable future. The weighted average risk-free interest rate is the implied yield currently available on zero-coupon government issues with a remaining term equal to the expected term.
	Weighted Average Assumptions for Stock Option Awards Granted to
	Employees and Directors under the Incentive Plan
		2014			2013
	Expected Life in Years		5.5			4.6
	Expected Volatility		87	%		83	%
	Expected Dividend Yield		0	%		0	%
	Risk-Free Interest Rate		1.6	%		0.6	%
	Employee Stock Purchase Plan
	The Company has reserved a total of 975 shares of common stock to be purchased under the ESPP, of which 59 shares remain available for purchase at March 31, 2014. Eligible employees may authorize up to 15% of their salary to purchase common stock at the lower of 85% of the beginning or 85% of the ending price during six-month purchase intervals. No more than 3 shares may be purchased by any one employee at the six-month purchase dates and no employee may purchase stock having a fair market value at the commencement date of $25 or more in any one calendar year. The Company issued 28 shares during the first three months of 2014 under the ESPP. Compensation expense for shares purchased under the ESPP related to the purchase discount and the “look-back” option were determined using a Black-Scholes option pricing model.

Collaborative_and_Other_Resear

Collaborative and Other Research and Development Contracts	3 Months Ended
	Mar. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Collaborative and Other Research and Development Contracts	'
	Note 3 — Collaborative and Other Research and Development Contracts
	U.S. Department of Health and Human Services (“BARDA/HHS”). In January 2007, the U.S. Department of Health and Human Services (“BARDA/HHS”) awarded the Company a $102,661 contract for the advanced development of peramivir for the treatment of influenza. During 2009, peramivir clinical development shifted to focus on intravenous delivery and the treatment of hospitalized patients. To support this focus, a September 2009 contract modification was awarded to increase funding by $77,191. On February 24, 2011, the Company announced that BARDA/HHS had awarded it a $55,000 contract modification, intended to fund completion of the Phase 3 development of i.v. peramivir for the treatment of patients hospitalized with influenza. This contract modification brings the total award from BARDA/HHS to $234,852 and provides funding to support the filing of a new drug application (“NDA”) to seek regulatory approval for i.v. peramivir in the U.S. The contract’s current expiration date is May 31, 2014. In December 2013, BioCryst submitted a NDA filing for i.v. peramivir to the U.S. Food & Drug Administration (“FDA”) seeking an indication as the first i.v. neuraminidase inhibitor approved in the U.S. for the treatment of acute uncomplicated influenza in adults. On February 24, 2014, the FDA notified the Company its NDA submission had been accepted for review. The FDA is expected to take action on the application by December 23, 2014.
	National Institute of Allergy and Infectious Diseases (“NIAID/HHS”). In September 2013, NIAID/HHS contracted with the Company for the development of BCX4430 as a treatment for Marburg virus disease. NIAID/HHS, part of the National Institutes of Health, made an initial award of $5.0 million to the Company. The total funding under this contract could be up to $22.0 million, if all contract options are exercised by NIAID/HHS, over a five year period. The goals of this contract are to file initial new drug (“IND”) applications for i.v. and intramuscular (“i.m.”) BCX4430 for the treatment of Marburg virus disease, and to conduct an initial Phase 1 human clinical trial. The aggregate $22.0 million contract and option funding supports the appropriate IND-enabling program and the initial clinical trial. As of March 31, 2014, a total of $7.5 million has been awarded under exercised options within the contract. BCX4430 is the lead compound in the Company’s broad spectrum antiviral (“BSAV”) research program.
	The contracts with BARDA/HHS and NIAID/HHS are cost-plus-fixed-fee contracts. That is, the Company is entitled to receive reimbursement for all costs incurred in accordance with the contracts’ provisions that are related to the development of peramivir and BCX4430 plus a fixed fee, or profit. BARDA/HHS and NIAID/HHS will make periodic assessments of progress, and the continuation of the contract is based on the Company’s performance, the timeliness and quality of deliverables, and other factors. The government has rights under certain contract clauses to terminate these contracts. These contracts are terminable by the government at any time for breach or without cause.
	Shionogi & Co., Ltd. (“Shionogi”). In March 2007, the Company entered into an exclusive license agreement with Shionogi to develop and commercialize peramivir in Japan for the treatment of seasonal and potentially life-threatening human influenza. Under the terms of the agreement, Shionogi obtained rights to injectable formulations of peramivir in Japan. The Company developed peramivir under a license from UAB and will owe sublicense payments to them on any future milestone payments and/or royalties received by the Company from Shionogi. In October 2008, the Company and Shionogi amended the license agreement to expand the territory covered by the agreement to include Taiwan and to provide rights for Shionogi to perform a Phase 3 clinical trial in Hong Kong. Shionogi has commercially launched peramivir under the commercial name RAPIACTA® in Japan.
	Green Cross Corporation (“Green Cross”). In June 2006, the Company entered into an agreement with Green Cross to develop and commercialize peramivir in Korea. Under the terms of the agreement, Green Cross will be responsible for all development, regulatory, and commercialization costs in Korea. The license provides that the Company will share in profits resulting from the sale of peramivir in Korea, including the sale of peramivir to the Korean government for stockpiling purposes. Furthermore, Green Cross will pay the Company a premium over its cost to supply peramivir for development and any future marketing of peramivir products in Korea.
	Mundipharma International Holdings Limited (“Mundipharma”). In February 2006, the Company entered into an exclusive, royalty bearing right and license agreement with Mundipharma for the development and commercialization of forodesine, a Purine Nucleoside Phosphorylase (“PNP”) inhibitor, for use in oncology (the “Original Agreement”). Under the terms of the license agreement, as amended, Mundipharma obtained worldwide rights to forodesine.
	Albert Einstein College of Medicine of Yeshiva University and Industrial Research, Ltd. (“AECOM” and “IRL” respectively). In June 2000, the Company licensed a series of potent inhibitors of PNP from AECOM and IRL, (collectively, the “Licensors”). The lead product candidates from this collaboration are forodesine and ulodesine. The Company has obtained worldwide exclusive rights to develop and ultimately distribute these, or any other, product candidates that might arise from research on these inhibitors. The Company has the option to expand its license agreement with the Licensors to include other inventions in the field made by the investigators or employees of the Licensors. The Company agreed to use commercially reasonable efforts to develop these drugs. In addition, the Company has agreed to pay certain milestone payments for each licensed product (which range in the aggregate from $1,400 to almost $4,000 per indication) for future development of these inhibitors, single digit royalties on net sales of any resulting product made by the Company, and to share approximately one quarter of future payments received from other third-party partners, if any. In addition, the Company has agreed to pay annual license fees, which can range from $150 to $500, that are creditable against actual royalties and other payments due to the Licensors. This agreement may be terminated by the Company at any time by giving 60 days advance notice or in the event of material uncured breach by the Licensors.
	In May 2010, the Company amended the license agreement through which the Company obtained worldwide exclusive rights to develop and ultimately distribute any product candidates that might arise from research on a series of PNP inhibitors, including forodesine and ulodesine. Under the terms of the amendment, the Licensors agreed to accept a reduction of one-half in the percentage of future payments received from third-party sub licensees of the licensed PNP inhibitors that must be paid to the Licensors. This reduction does not apply to (i) any milestone payments the Company may receive in the future under its license agreement with Mundipharma and (ii) royalties received from its sub licensees in connection with the sale of licensed products, for which the original payment rate will remain in effect. The rate of royalty payments to the Licensors based on net sales of any resulting product made by the Company remains unchanged.
	In consideration for these modifications in 2010, the Company issued to the Licensors shares of its common stock with an aggregate value of $5,911 and paid the Licensors $90 in cash. Additionally, at the Company’s sole option and subject to certain agreed upon conditions, any future non-royalty payments due to be paid by the Company to the Licensors under the license agreement may be made either in cash, in shares of the Company’s common stock, or in a combination of cash and shares.
	On November 17, 2011, the Company further amended its agreements with the Licensors whereby the Licensors agreed to accept a reduction of one-half in the percentage of Net Proceeds (as defined in the license agreement) received by the Company under its Amended and Restated Agreement with Mundipharma that will be paid to AECOM/IRL.
	On June 19, 2012, the Company further amended its agreements with the Licensors whereby the parties clarified the definition of the field with respect to PNP inhibition and the Licensors agreed to grant an exclusive worldwide license of BCX4430 to BioCryst for any antiviral use.
	At its sole option and subject to certain agreed upon conditions, any future non-royalty payments due to be paid by the Company to the Licensors under the license agreement may be made either in cash, in shares of the Company’s common stock, or in a combination of cash and shares.
	The University of Alabama at Birmingham (“UAB”). The Company currently has agreements with UAB for influenza neuraminidase and complement inhibitors. Under the terms of these agreements, UAB performed specific research for the Company in return for research payments and license fees. UAB has granted the Company certain rights to any discoveries in these areas resulting from research developed by UAB or jointly developed with the Company. The Company has agreed to pay single digit royalties on sales of any resulting product and to share in future payments received from other third-party partners. The Company has completed the research under the UAB agreements. These two agreements have initial 25-year terms, are automatically renewable for five-year terms throughout the life of the last patent and are terminable by the Company upon three months’ notice and by UAB under certain circumstances. Upon termination both parties shall cease using the other parties’ proprietary and confidential information and materials, the parties shall jointly own joint inventions and UAB shall resume full ownership of all UAB licensed products. There is currently no activity between the Company and UAB on these agreements, but when the Company licenses this technology, such as in the case of the Shionogi and Green Cross agreements, or commercializes products related to these programs, the Company will owe sublicense fees or royalties on amounts it receives.

Royalty_Monetization

Royalty Monetization	3 Months Ended
	Mar. 31, 2014
Text Block [Abstract]	'
Royalty Monetization	'
	Note 4 — Royalty Monetization
	Overview
	On March 9, 2011, the Company completed a $30,000 financing transaction to monetize certain future royalty and milestone payments under the Shionogi Agreement, pursuant to which Shionogi licensed from the Company the rights to market RAPIACTA® in Japan and, if approved for commercial sale, Taiwan. The Company received net proceeds of $22,691 from this transaction.
	As part of the transaction, the Company entered into a purchase and sale agreement dated as of March 9, 2011 with Royalty Sub, whereby the Company transferred to Royalty Sub, among other things, (i) its rights to receive certain royalty and milestone payments from Shionogi arising under the Shionogi Agreement, and (ii) the right to receive payments under a Japanese yen/US dollar foreign currency hedge arrangement (as further described below, the “Currency Hedge Agreement”) put into place by the Company in connection with the transaction. Royalty payments will be paid by Shionogi in Japanese yen and milestone payments will paid in U.S. dollars. The Company’s collaboration with Shionogi was not impacted as a result of this transaction.
	Non-Recourse Notes Payable
	On March 9, 2011, Royalty Sub completed a private placement to institutional investors of $30,000 in aggregate principal amount of its PhaRMA Senior Secured 14.0% Notes due 2020 (the “PhaRMA Notes”). The PhaRMA Notes were issued by Royalty Sub under an Indenture, dated as of March 9, 2011 (the “Indenture”), by and between Royalty Sub and U.S. Bank National Association, as Trustee. Principal and interest on the PhaRMA Notes issued are payable from, and are secured by, the rights to royalty and milestone payments under the Shionogi Agreement transferred by the Company to Royalty Sub and payments, if any, made to Royalty Sub under the Currency Hedge Agreement. The PhaRMA Notes bear interest at 14% per annum, payable annually in arrears on September 1st of each year (the “Payment Date”). The Company remains entitled to receive any royalties and milestone payments related to sales of peramivir by Shionogi following repayment of the PhaRMA Notes.
	Royalty Sub’s obligations to pay principal and interest on the PhaRMA Notes are obligations solely of Royalty Sub and are without recourse to any other person, including the Company, except to the extent of the Company’s pledge of its equity interests in Royalty Sub in support of the PhaRMA Notes. The Company may, but is not obligated to, make capital contributions to a capital account that may be used to redeem, or on up to one occasion pay any interest shortfall on, the PhaRMA Notes.
	In September 2013, Royalty Sub paid $1,844 of interest on the PhaRMA Notes from royalty payments received from RAPIACTA® sales from the preceding four calendar quarters. This payment resulted in an obligation shortfall of approximately $2,356 associated with accrued interest due September 3, 2013. As stipulated under the PhaRMA Notes Indenture, if the amount available for payment on any Payment Date is insufficient to pay all of the interest due on a Payment Date, the shortfall in interest will accrue interest at the interest rate applicable to the PhaRMA Notes compounded annually. Accordingly, commencing in September 2013, the Company began accruing interest at 14% per annum on the interest shortfall of $2,356. In March 2014, Royalty Sub paid an additional $446 of interest, bringing the shortfall down to $2,099 as of March 31, 2014. Under the terms of the Indenture, Royalty Sub’s inability to pay the full amount of interest payable in September 2013 did not constitute an event of default under the PhaRMA Notes unless the shortfall, plus interest thereon, is not satisfied on the next succeeding Payment Date for the PhaRMA Notes, which is September 1, 2014. Based upon RAPIACTA® sales to date provided to the Company by Shionogi, the Company cannot guarantee sufficient royalties will be available to fund the interest shortfall prior to September 1, 2014. Should these royalties be insufficient to cover the interest shortfall, the PhaRMA Notes will be in default as of September 1, 2014. If an event of default were to occur under the PhaRMA Notes, the holders of the PhaRMA Notes may be able to foreclose on the collateral securing the PhaRMA Notes and our equity interest in Royalty Sub and exercise other remedies available to them under the indenture in respect of the PhaRMA Notes. In such event, we may not realize the benefit of future royalty payments that might otherwise accrue to us following repayment of the PhaRMA Notes and we might otherwise be adversely affected.
	The Indenture does not contain any financial covenants. The Indenture includes customary representations and warranties of Royalty Sub, affirmative and negative covenants of Royalty Sub, Events of Default and related remedies, and provisions regarding the duties of the Trustee, indemnification of the Trustee, and other matters typical for indentures used in structured financings of this type.
	As of March 31, 2014, the aggregate fair value of the PhaRMA Notes approximates its carrying value of $30,000. The estimated fair value of the PhaRMA Notes is classified as Level 2 in the fair value hierarchy as defined in U.S. GAAP. The PhaRMA Notes are redeemable at the option of Royalty Sub at any time at a redemption price equal to 100% of the outstanding principal balance of the PhaRMA Notes being redeemed, plus accrued and unpaid interest through the redemption date on the PhaRMA Notes being redeemed.
	Foreign Currency Hedge
	In connection with the issuance by Royalty Sub of the PhaRMA Notes, the Company entered into a Currency Hedge Agreement to hedge certain risks associated with changes in the value of the Japanese yen relative to the U.S. dollar. Under the Currency Hedge Agreement, the Company has the right to purchase dollars and sell yen at a rate of 100 yen per dollar for which the Company may be required to pay a premium in each year from 2014 through 2020, provided the Currency Hedge Agreement remains in effect. A payment of $1,950 will be required if, on May 18 of the relevant year, the U.S. dollar is worth 100 yen or less as determined in accordance with the Currency Hedge Agreement.
	The Currency Hedge Agreement does not qualify for hedge accounting treatment; therefore, mark-to-market adjustments are recognized in the Company’s Consolidated Statement of Comprehensive Loss. Cumulative mark-to-market adjustments for the three months ended March 31, 2014 and 2013 resulted in a loss of $1,526 and a gain of $1,957, respectively. The Company is also required to post collateral in connection with the mark-to-market adjustments based on defined thresholds. As of March 31, 2014, $1,530 was posted under the Currency Hedge Agreement. The Company will not be required at any time to post collateral exceeding the maximum premium payments remaining payable under the Currency Hedge Agreement. Subject to certain obligations the Company has in connection with the PhaRMA Notes, the Company has the right to terminate the Currency Hedge Agreement with respect to the 2016 through 2020 period by giving notice to the counterparty prior to May 18, 2014 and payment of a $1,950 termination fee. If the Company terminates the hedge agreement with respect to currency hedges for 2016 through 2020, the maximum obligation under the currency hedge is $5,850, including the $1,950 termination fee. If the Company lets the termination right lapse, the maximum amount of hedge collateral the Company would be required to post is $13,650. The Company is required to maintain a foreign currency hedge at 100 yen per dollar under the agreements governing the PhaRMA Notes.

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stockholders' Equity	'
	Note 5 — Stockholders’ Equity
	In June 2011, the Company entered into an At Market Issuance Sales Agreement (the “ATM Agreement”) with McNicoll, Lewis & Valak (“MLV”) pursuant to which the Company may issue and sell $70,000 in shares of its common stock at current market prices under a Form S-3 registration statement with MLV acting as the sales agent. Subject to the terms and conditions of the ATM Agreement, MLV will use commercially reasonable efforts to sell the Company’s common stock from time to time, based upon the Company’s instruction, including any price, time or size limits or other customary parameters or conditions the Company may impose. The Company will pay MLV an aggregate commission rate of 2% of the gross proceeds of the sales price per share of any common stock sold under the Agreement depending on the number of shares sold. On June 28, 2011, the Company filed a Registration Statement on Form S-3, which became effective on July 13, 2011, for the issuance and sale of up to $70,000 of equity or other securities. During the three months ended March 31, 2013, the Company sold an aggregate of 301 shares of common stock at an average per share price of $1.37 pursuant to the Agreement for net proceeds of $360.
	In August 2013, the Company completed a public offering of 4,600 shares of its common stock at a price of $4.40 per share, which included the underwriters’ over-allotment allocation of an additional 600 shares. Net proceeds were approximately $18,500 after deducting underwriting discounts and offering expenses.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
The Company	'
	The Company
	BioCryst Pharmaceuticals, Inc. (the “Company”) is a biotechnology company that designs, optimizes and develops novel drugs that block key enzymes involved in the pathogenesis of diseases. The Company focuses on rare and infectious diseases in which unmet medical needs exist and that are aligned with its capabilities and expertise. The Company was incorporated in Delaware in 1986 and its headquarters is located in Durham, North Carolina. The Company integrates the disciplines of biology, crystallography, medicinal chemistry and computer modeling to discover and develop small molecule pharmaceuticals through the process known as structure-guided drug design. BioCryst has incurred losses and negative cash flows from operations since inception.
	Based on its current operating plans, the Company expects it has sufficient liquidity, with its existing cash and investments of $34,220, to continue its planned operations into the first quarter of 2015. The Company’s liquidity needs, and ability to address those needs, will largely be determined by the success of its product candidates and key development and regulatory events in the future. In order to continue its operations substantially beyond the first quarter of 2015 it will need to: (1) successfully secure or increase U.S. Government funding of its programs; (2) out-license rights to certain of its product candidates, pursuant to which the Company would receive cash milestones; (3) raise additional capital through equity or debt financings or from other sources; (4) obtain product candidate regulatory approvals, which would generate revenue and cash flow; (5) reduce spending on one or more research and development programs; and/or (6) restructure operations. The Company will continue to incur operating losses and negative cash flows until revenues reach a level sufficient to support ongoing operations.
Basis of Presentation	'
	Basis of Presentation
	Beginning in March 2011, the consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, JPR Royalty Sub LLC (“Royalty Sub”). Royalty Sub was formed in connection with a $30,000 financing transaction the Company completed on March 9, 2011. See Note 4, Royalty Monetization, for a further description of this transaction. All intercompany transactions and balances have been eliminated.
	The Company’s consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial reporting and the instructions to Form 10-Q and do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. Such financial statements reflect all adjustments that are, in management’s opinion, necessary to present fairly, in all material respects, the Company’s consolidated financial position, results of operations, and cash flows. There were no adjustments other than normal recurring adjustments.
	These financial statements should be read in conjunction with the financial statements for the year ended December 31, 2013 and the notes thereto included in the Company’s 2013 Annual Report on Form 10-K. Interim operating results are not necessarily indicative of operating results for the full year. The balance sheet as of December 31, 2013 has been derived from the audited consolidated financial statements included in the Company’s most recent Annual Report on Form 10-K.
Reclassifications	'
	Reclassifications
	In the first quarter of 2014, the Company changed its classification of patent costs. This change resulted in $196 of patent expenses being reclassified from research and development expense to general and administrative expense for the three months ended March 31, 2013. This reclassification had no effect on previously reported total operating expenses or net loss amounts.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	The Company generally considers cash equivalents to be all cash held in commercial checking accounts, money market accounts or investments in debt instruments with maturities of three months or less at the time of purchase. The carrying value of cash and cash equivalents approximates fair value due to the short-term nature of these items.
Restricted Cash	'
	Restricted Cash
	Restricted cash as of March 31, 2014 reflects $150 the Company is required to maintain in an interest bearing certificate of deposit to serve as collateral for a corporate credit card program.
Investments	'
	Investments
	The Company invests in high credit quality investments in accordance with its investment policy, which is designed to minimize the possibility of loss. The objective of the Company’s investment policy is to ensure the safety and preservation of invested funds, as well as maintaining liquidity sufficient to meet cash flow requirements. The Company places its excess cash with high credit quality financial institutions, commercial companies, and government agencies in order to limit the amount of its credit exposure. Per its policy, the Company is able to invest in marketable debt securities that may consist of U.S. Government and government agency securities, money market and mutual fund investments, municipal and corporate notes and bonds, commercial paper and asset or mortgage-backed securities, among others. The Company’s investment policy requires it to purchase high-quality marketable securities with a maximum individual maturity of three years and requires an average portfolio maturity of no more than 18 months. Some of the securities the Company invests in may have market risk. This means that a change in prevailing interest rates may cause the principal amount of the investment to fluctuate. To minimize this risk, the Company schedules its investments with maturities that coincide with expected cash flow needs, thus avoiding the need to redeem an investment prior to its maturity date. Accordingly, the Company does not believe it has a material exposure to interest rate risk arising from its investments. Generally, the Company’s investments are not collateralized. The Company has not realized any significant losses from its investments.
	The Company classifies all of its investments as available-for-sale. Unrealized gains and losses on investments are recognized in comprehensive income/(loss), unless an unrealized loss is considered to be other than temporary, in which case the unrealized loss is charged to operations. The Company periodically reviews its investments for other than temporary declines in fair value below cost basis and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The Company believes the individual unrealized losses represent temporary declines primarily resulting from interest rate changes. Realized gains and losses are reflected in interest and other income in the Consolidated Statements of Comprehensive Loss and are determined using the specific identification method with transactions recorded on a settlement date basis. Investments with original maturities at date of purchase beyond three months and which mature at or less than 12 months from the balance sheet date are classified as current. Investments with a maturity beyond 12 months from the balance sheet date are classified as long-term. At March 31, 2014, the Company believes that the costs of its investments are recoverable in all material respects.
	The following tables summarize the fair value of the Company’s investments by type. The estimated fair value of the Company’s fixed income investments are classified as Level 2 in the fair value hierarchy as defined in U.S. GAAP. These fair values are obtained from independent pricing services which utilize Level 2 inputs.
			March 31, 2014
			Amortized		Accrued		Gross		Gross		Estimated
			Cost		Interest		Unrealized		Unrealized		Fair Value
							Gains		Losses
	Obligations of U.S. Government and its agencies		$	4,800	$	1	$	—	$	1	$	4,800
	Corporate debt securities			6,045		46		2		1		6,092
	Commercial paper			9,592		—		2		—		9,594
	Total investments		$	20,437	$	47	$	4	$	2	$	20,486
			December 31, 2013
			Amortized		Accrued		Gross		Gross		Estimated
			Cost		Interest		Unrealized		Unrealized		Fair Value
							Gains		Losses
	Obligations of U.S. Government and its agencies		$	4,899	$	1	$	1	$	—	$	4,901
	Corporate debt securities			8,528		47		2		1		8,576
	Commercial paper			5,994		—		2		—		5,996
	Total investments		$	19,421	$	48	$	5	$	1	$	19,473
	The following table summarizes the scheduled maturity for the Company’s investments at March 31, 2014 and December 13, 2013.
			2014		2013
	Maturing in one year or less		$	17,807	$	16,891
	Maturing after one year through two years			2,679		2,582
	Total investments		$	20,486	$	19,473
Receivables	'
	Receivables
	Receivables are recorded for amounts due to the Company related to reimbursable research and development costs from the U.S. Department of Health and Human Services or royalty receivables from Shionogi & Co. Ltd. At March 31, 2014 and December 31, 2013, the Company had the following receivables.
			March 31, 2014
			Billed		Unbilled		Total
	U.S. Department of Health and Human Services		$	195	$	1,270	$	1,465
	Shionogi & Co. Ltd.			1,815		—		1,815
	Total receivables		$	2,010	$	1,270	$	3,280
			December 31, 2013
			Billed		Unbilled		Total
	U.S. Department of Health and Human Services		$	90	$	1,573	$	1,663
	Shionogi & Co. Ltd.			452		—		452
	Total receivables		$	542	$	1,573	$	2,115
	Monthly invoices are submitted to the U.S. Department of Health and Human Services related to reimbursable research and development costs. The Company is also entitled to monthly reimbursement of indirect costs based on rates stipulated in the underlying contract. The Company’s calculations of its indirect cost rates are subject to audit by the federal government.
Patents and Licenses	'
	Patents and Licenses
	The Company seeks patent protection on internally developed processes and products. All patent related costs are expensed to general and administrative expenses when incurred as recoverability of such expenditures is uncertain.
Accrued Expenses	'
	Accrued Expenses
	The Company generally enters into contractual agreements with third-party vendors who provide research and development, manufacturing, and other services in the ordinary course of business. Some of these contracts are subject to milestone-based invoicing and services are completed over an extended period of time. The Company records liabilities under these contractual commitments when it determines an obligation has been incurred, regardless of the timing of the invoice. This process involves reviewing open contracts and purchase orders, communicating with applicable Company personnel to identify services that have been performed on its behalf and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of actual cost. The majority of service providers invoice the Company monthly in arrears for services performed. The Company makes estimates of accrued expenses as of each balance sheet date in its financial statements based on the facts and circumstances. The Company periodically confirms the accuracy of its estimates with the service providers and makes adjustments if necessary. Examples of estimated accrued expenses include:
		•		fees paid to Clinical Research Organizations (“CROs”) in connection with preclinical and toxicology studies and clinical trials;
		•		fees paid to investigative sites in connection with clinical trials;
		•		fees paid to contract manufacturers in connection with the production of our raw materials, drug substance and drug products; and
		•		professional fees.
	The Company bases its expenses related to clinical trials on its estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and clinical research organizations that conduct and manage clinical trials on the Company’s behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Accrued expenses as of March 31, 2014 and December 31, 2013 included $2,076 and $2,210, respectively, of research and development costs.
Income Taxes	'
	Income Taxes
	The liability method is used in the Company’s accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse.
Accumulated Other Comprehensive (Loss) Income	'
	Accumulated Other Comprehensive (Loss) Income
	Accumulated other comprehensive (loss) income is comprised of unrealized gains and losses on investments available-for-sale and is disclosed as a separate component of stockholders’ equity. No reclassifications out of accumulated other comprehensive (loss) income were recorded during the three months ended March 31, 2014 and 2013.
Revenue Recognition	'
	Revenue Recognition
	The Company recognizes revenues from collaborative and other research and development arrangements and product sales. Revenue is realized or realizable and earned when all of the following criteria are met: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the seller’s price to the buyer is fixed or determinable; and (iv) collectability is reasonably assured.
	Collaborative and Other Research and Development Arrangements and Royalties
	Revenue from license fees, royalty payments, event payments, and research and development fees are recognized as revenue when the earnings process is complete and the Company has no further continuing performance obligations or the Company has completed the performance obligations under the terms of the agreement. Fees received under licensing agreements that are related to future performance are deferred and recognized over an estimated period determined by management based on the terms of the agreement and the products licensed. In the event a license agreement contains multiple deliverables, the Company evaluates whether the deliverables are separate or combined units of accounting. Revisions to revenue or profit estimates as a result of changes in the estimated revenue period are recognized prospectively.
	Under certain of our license agreements, the Company receives royalty payments based upon our licensees’ net sales of covered products. The Company recognizes royalty revenues when it can reliably estimate such amounts and collectability is reasonably assured.
	Reimbursements received for direct out-of-pocket expenses related to research and development costs are recorded as revenue in the Consolidated Statements of Comprehensive Loss rather than as a reduction in expenses. Event payments are recognized as revenue upon the achievement of specified events if (1) the event is substantive in nature and the achievement of the event was not reasonably assured at the inception of the agreement and (2) the fees are non-refundable and non-creditable. Any event payments received prior to satisfying these criteria are recorded as deferred revenue. Under the Company’s contracts with the U.S. Department of Health and Human Services, (“BARDA/HHS”), and the National Institute of Allergy and Infectious Diseases (“NIAID/HHS”), revenue is recognized as reimbursable direct and indirect costs are incurred.
	Product Sales
	Sales are recognized when there is persuasive evidence that an arrangement exists, title has passed, the price was fixed and determinable, and collectability is reasonably assured. Product sales are recognized net of estimated allowances, discounts, sales returns, chargebacks and rebates.
	The Company recorded the following revenues for the three months ended March 31, 2014 and 2013:
			2014		2013
	Royalty revenue		$	1,821	$	1,924
	Collaborative and other research and development revenues:
	U.S. Department of Health and Human Services			1,341		1,334
	Shionogi (Japan)			296		296
	Total revenues		$	3,458	$	3,554
Collaborative and Other Research and Development Arrangements and Royalties	'
	Collaborative and Other Research and Development Arrangements and Royalties
	Revenue from license fees, royalty payments, event payments, and research and development fees are recognized as revenue when the earnings process is complete and the Company has no further continuing performance obligations or the Company has completed the performance obligations under the terms of the agreement. Fees received under licensing agreements that are related to future performance are deferred and recognized over an estimated period determined by management based on the terms of the agreement and the products licensed. In the event a license agreement contains multiple deliverables, the Company evaluates whether the deliverables are separate or combined units of accounting. Revisions to revenue or profit estimates as a result of changes in the estimated revenue period are recognized prospectively.
	Under certain of our license agreements, the Company receives royalty payments based upon our licensees’ net sales of covered products. The Company recognizes royalty revenues when it can reliably estimate such amounts and collectability is reasonably assured.
	Reimbursements received for direct out-of-pocket expenses related to research and development costs are recorded as revenue in the Consolidated Statements of Comprehensive Loss rather than as a reduction in expenses. Event payments are recognized as revenue upon the achievement of specified events if (1) the event is substantive in nature and the achievement of the event was not reasonably assured at the inception of the agreement and (2) the fees are non-refundable and non-creditable. Any event payments received prior to satisfying these criteria are recorded as deferred revenue. Under the Company’s contracts with the U.S. Department of Health and Human Services, (“BARDA/HHS”), and the National Institute of Allergy and Infectious Diseases (“NIAID/HHS”), revenue is recognized as reimbursable direct and indirect costs are incurred.
Product Sales	'
	Product Sales
	Sales are recognized when there is persuasive evidence that an arrangement exists, title has passed, the price was fixed and determinable, and collectability is reasonably assured. Product sales are recognized net of estimated allowances, discounts, sales returns, chargebacks and rebates.
	The Company recorded the following revenues for the three months ended March 31, 2014 and 2013:
			2014		2013
	Royalty revenue		$	1,821	$	1,924
	Collaborative and other research and development revenues:
	U.S. Department of Health and Human Services			1,341		1,334
	Shionogi (Japan)			296		296
	Total revenues		$	3,458	$	3,554
Research and Development Expenses	'
	Research and Development Expenses
	The Company’s research and development costs are charged to expense when incurred. Research and development expenses include all direct and indirect development costs related to the development of the Company’s portfolio of product candidates. Advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are recognized as expense when the related goods are delivered or the related services are performed. Research and development expenses include, among other items, personnel costs, including salaries and benefits, manufacturing costs, clinical, regulatory, and toxicology services performed by CROs, materials and supplies, and overhead allocations consisting of various administrative and facilities related costs. Most of the Company’s manufacturing and clinical and preclinical studies are performed by third-party CROs. Costs for studies performed by CROs are accrued by the Company over the service periods specified in the contracts and estimates are adjusted, if required, based upon the Company’s on-going review of the level of services actually performed.
	Additionally, the Company has license agreements with third parties, such as Albert Einstein College of Medicine of Yeshiva University (“AECOM”), Industrial Research, Ltd. (“IRL”), and the University of Alabama at Birmingham (“UAB”), which require fees related to sublicense agreements or maintenance fees. The Company expenses sublicense payments as incurred unless they are related to revenues that have been deferred, in which case the expenses are deferred and recognized over the related revenue recognition period. The Company expenses maintenance payments as incurred.
	Deferred collaboration expenses represent sub-license payments, paid to the Company’s academic partners upon receipt of consideration from various commercial partners, and other consideration paid to our academic partners for modification to existing license agreements. These deferred expenses would not have been incurred without receipt of such payments or modifications from the Company’s commercial partners and are being expensed in proportion to the related revenue being recognized. The Company believes that this accounting treatment appropriately matches expenses with the associated revenue.
Stock-Based Compensation	'
	Stock-Based Compensation
	All share-based payments, including grants of stock option awards and restricted stock awards, are recognized in the Company’s Consolidated Statements of Comprehensive Loss based on their fair values. The fair value of stock option awards is estimated using the Black-Scholes option pricing model. The fair value of restricted stock awards is based on the grant date closing price of the common stock. Stock-based compensation cost is recognized as expense on a straight-line basis over the requisite service period of the award.
Interest Expense and Deferred Financing Costs	'
	Interest Expense and Deferred Financing Costs
	Interest expense for the three months ended March 31, 2014 and 2013 was $1,242 and $1,180, respectively, and relates to the issuance of the PhaRMA Notes (defined in Note 4). Costs directly associated with the issuance of the PhaRMA Notes have been capitalized and are included in other non-current assets on the Consolidated Balance Sheets. These costs are being amortized to interest expense over the term of the PhaRMA Notes using the effective interest rate method. Amortization of deferred financing costs included in interest expense was $110 for each of the three months ended March 31, 2014 and 2013.
Currency Hedge Agreement	'
	Currency Hedge Agreement
	In connection with the issuance by Royalty Sub of the PhaRMA Notes, the Company entered into a Currency Hedge Agreement (defined in Note 4) to hedge certain risks associated with changes in the value of the Japanese yen relative to the U.S. dollar. The Currency Hedge Agreement does not qualify for hedge accounting treatment; therefore, mark-to-market adjustments are recognized in the Company’s Consolidated Statements of Comprehensive Loss. Cumulative mark-to-market adjustments for the three months ended March 31, 2014 and 2013 resulted in a loss of $1,526 and a gain of $1,957, respectively. Mark-to-market adjustments are determined by a third party pricing model that uses quoted prices in markets that are not actively traded and for which significant inputs are observable directly or indirectly, representing Level 2 in the fair value hierarchy as defined by U.S. GAAP. The Company is also required to post collateral in connection with the mark-to-market adjustments based on thresholds defined in the Currency Hedge Agreement. As of March 31, 2014, $1,530 of hedge collateral was posted under the agreement. No hedge collateral was posted under the agreement as of December 31, 2013.
Net Loss Per Share	'
	Net Loss Per Share
	Net loss per share is based upon the weighted average number of common shares outstanding during the period. Diluted loss per share is equivalent to basic net loss per share for all periods presented herein because common equivalent shares from unexercised stock options and common shares expected to be issued under the Company’s employee stock purchase plan were anti-dilutive. The calculation of diluted earnings per share for the three months ended March 31, 2014 and 2013 does not include 5,206 and 681, respectively, of such potential common shares, as their impact would be anti-dilutive.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements. Actual results could differ from those estimates.
Concentration of Market Risk	'
	Concentration of Market Risk
	The reimbursement of peramivir and BCX4430 development expenses is a significant source of the Company’s revenue and one which has an underlying cash flow stream. This revenue and cash flow is earned under cost-plus-fixed-fee contracts with BARDA/HHS and NIAID/HHS, respectively. The Company relies on BARDA/HHS and NIAID/HHS to reimburse predominantly all of the development costs for its peramivir and BCX4430 programs, respectively. Accordingly, reimbursement of these expenses represents a significant portion of the Company’s collaborative and other research and development revenues. The completion and/or termination of these programs/collaborations could negatively impact the Company’s future Consolidated Statements of Comprehensive Loss and Cash Flows. In addition, the Company also recognizes royalty revenue from the net sales of RAPIACTA®; however, the underlying cash flow from these royalty payments goes directly to pay the interest, and then the principal, on the Company’s non-recourse notes payable. Payment of the interest and the ultimate repayment of principal of these notes will be entirely funded by future royalty payments derived from net sales of RAPIACTA®. At March 31, 2014, there was a significant underpayment of interest on the PhaRMA Notes, which if unpaid at September 1, 2014, will constitute an event of default under the PhaRMA Notes. If an event of default were to occur under the PhaRMA Notes, the holders of the PhaRMA Notes may be able to foreclose on the collateral securing the PhaRMA Notes and our equity interest in Royalty Sub and exercise other remedies available to them under the indenture in respect of the PhaRMA Notes. In such event, we may not realize the benefit of future royalty payments that might otherwise accrue to us following repayment of the PhaRMA Notes and we might otherwise be adversely affected. The Company’s drug development activities are performed by a limited group of third party vendors. If any of these vendors were unable to perform their services, this could significantly impact the Company’s ability to complete its drug development activities.
Credit Risk	'
	Credit Risk
	Cash equivalents and investments are financial instruments which potentially subject the Company to concentration of risk to the extent recorded on the Consolidated Balance Sheets. The Company deposits excess cash with major financial institutions in the United States. Balances may exceed the amount of insurance provided on such deposits. The Company believes it has established guidelines for investment of its excess cash relative to diversification and maturities that maintain safety and liquidity. To minimize the exposure due to adverse shifts in interest rates, the Company maintains a portfolio of investments with an average maturity of approximately 24 months or less. The majority of the Company’s receivables are due from the U.S. Government, for which there is no assumed credit risk.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	There have been no recent accounting pronouncements or changes in accounting pronouncements since the recent accounting pronouncements described in the Company’s 2013 Annual Report on Form 10-K that are of significance to the Company.

Significant_Accounting_Policie2

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Fair Value of the Company's Investments by Type	'
	The following tables summarize the fair value of the Company’s investments by type. The estimated fair value of the Company’s fixed income investments are classified as Level 2 in the fair value hierarchy as defined in U.S. GAAP. These fair values are obtained from independent pricing services which utilize Level 2 inputs.
		March 31, 2014
		Amortized		Accrued		Gross		Gross		Estimated
		Cost		Interest		Unrealized		Unrealized		Fair Value
						Gains		Losses
	Obligations of U.S. Government and its agencies	$	4,800	$	1	$	—	$	1	$	4,800
	Corporate debt securities		6,045		46		2		1		6,092
	Commercial paper		9,592		—		2		—		9,594
	Total investments	$	20,437	$	47	$	4	$	2	$	20,486
		December 31, 2013
		Amortized		Accrued		Gross		Gross		Estimated
		Cost		Interest		Unrealized		Unrealized		Fair Value
						Gains		Losses
	Obligations of U.S. Government and its agencies	$	4,899	$	1	$	1	$	—	$	4,901
	Corporate debt securities		8,528		47		2		1		8,576
	Commercial paper		5,994		—		2		—		5,996
	Total investments	$	19,421	$	48	$	5	$	1	$	19,473
Scheduled Maturity for the Company's Investments	'
	The following table summarizes the scheduled maturity for the Company’s investments at March 31, 2014 and December 13, 2013.
		2014		2013
	Maturing in one year or less	$	17,807	$	16,891
	Maturing after one year through two years		2,679		2,582
	Total investments	$	20,486	$	19,473
Summary of Receivables	'
	These receivables are evaluated to determine if any reserve or allowance should be established at each reporting date. At March 31, 2014 and December 31, 2013, the Company had the following receivables.
		March 31, 2014
		Billed		Unbilled		Total
	U.S. Department of Health and Human Services	$	195	$	1,270	$	1,465
	Shionogi & Co. Ltd.		1,815		—		1,815
	Total receivables	$	2,010	$	1,270	$	3,280
		December 31, 2013
		Billed		Unbilled		Total
	U.S. Department of Health and Human Services	$	90	$	1,573	$	1,663
	Shionogi & Co. Ltd.		452		—		452
	Total receivables	$	542	$	1,573	$	2,115
Summary of Revenues	'
	The Company recorded the following revenues for the three months ended March 31, 2014 and 2013:
		2014		2013
	Royalty revenue	$	1,821	$	1,924
	Collaborative and other research and development revenues:
	U.S. Department of Health and Human Services		1,341		1,334
	Shionogi (Japan)		296		296
	Total revenues	$	3,458	$	3,554

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Summary of Related Activity under Incentive Plan	'
	Related activity under the Incentive Plan is as follows:
		Awards			Options			Weighted
		Available			Outstanding			Average
								Exercise
								Price
	Balance December 31, 2013		1,082			8,986		$	4.99
	Restricted stock awards granted		(593	)		—			—
	Restricted stock awards cancelled		—			—			—
	Stock option awards granted		(391	)		391			10.79
	Stock option awards exercised		—			(832	)		5.18
	Stock option awards cancelled		—			—			—
	Balance March 31, 2014		98			8,545		$	5.24
Weighted Average Assumptions for Stock Option Awards Granted to Employees and Directors under the Incentive Plan	'
	Weighted Average Assumptions for Stock Option Awards Granted to
	Employees and Directors under the Incentive Plan
		2014			2013
	Expected Life in Years		5.5			4.6
	Expected Volatility		87	%		83	%
	Expected Dividend Yield		0	%		0	%
	Risk-Free Interest Rate		1.6	%		0.6	%

Significant_Accounting_Policie3

Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended					3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014	Mar. 09, 2011	Mar. 31, 2014	Mar. 31, 2014
				Money Market Funds [Member]	JPR Royalty Sub LLC [Member]	Maximum [Member]	Minimum [Member]
Significant Accounting Policies [Line Items]	'	'	'	'	'	'	'
Cash and investments	$34,220	'	'	'	'	'	'
Proceeds from non-recourse notes	'	'	'	'	30,000	'	'
Reclassification adjustments from research and development expense to general and administrative expense	196	'	'	'	'	'	'
Maturity of investments	'	'	'	'	'	'3 months	'
Restricted cash	150	'	151	150	'	'	'
Maturity period for high-quality marketable securities	'	'	'	'	'	'3 years	'
Average portfolio maturity period for high-quality marketable securities	'	'	'	'	'	'18 months	'
Maturity period of investments	'	'	'	'	'	'12 months	'3 months
Maturity period of longterm investments	'12 months	'	'	'	'	'	'
Accrued expenses	2,076	'	2,210	'	'	'	'
Accumulated Other comprehensive income (loss) reclassification	0	0	'	'	'	'	'
Interest expenses	1,242	1,180	'	'	'	'	'
Amortization of deferred financing costs	110	110	'	'	'	'	'
Cumulative mark-to-market adjustments - Gain/loss	-1,526	1,957	'	'	'	'	'
Hedge collateral under the agreement	$1,530	'	$0	'	'	'	'
Antidilutive effect of shares issued under employee Stock Purchase Plan	5,206	681	'	'	'	'	'
Average maturity for portfolio investments	'	'	'	'	'	'24 months	'

Significant_Accounting_Policie4

Significant Accounting Policies - Fair Value of the Company's Investments by Type (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Amortized Cost	$20,437	$19,421
Accrued Interest	47	48
Gross Unrealized Gains	4	5
Gross Unrealized Losses	2	1
Estimated Fair Value	20,486	19,473
Level 2 [Member] | Obligations of U.S. Government and its Agencies [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Amortized Cost	4,800	4,899
Accrued Interest	1	1
Gross Unrealized Gains	'	1
Gross Unrealized Losses	1	'
Estimated Fair Value	4,800	4,901
Level 2 [Member] | Corporate Debt Securities [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Amortized Cost	6,045	8,528
Accrued Interest	46	47
Gross Unrealized Gains	2	2
Gross Unrealized Losses	1	1
Estimated Fair Value	6,092	8,576
Level 2 [Member] | Commercial Paper [Member]	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Amortized Cost	9,592	5,994
Gross Unrealized Gains	2	2
Estimated Fair Value	$9,594	$5,996

Significant_Accounting_Policie5

Significant Accounting Policies - Scheduled Maturity for the Company's Investments (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Maturing in one year or less	$17,807	$16,891
Maturing after one year through two years	2,679	2,582
Estimated Fair Value	$20,486	$19,473

Significant_Accounting_Policie6

Significant Accounting Policies - Summary of Receivables (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	$3,280	$2,115
U.S. Department of Health and Human Services [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	1,465	1,663
Shionogi & Co. Ltd [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	1,815	452
Billed [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	2,010	542
Billed [Member] | U.S. Department of Health and Human Services [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	195	90
Billed [Member] | Shionogi & Co. Ltd [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	1,815	452
Unbilled [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	1,270	1,573
Unbilled [Member] | U.S. Department of Health and Human Services [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Line Items]	'	'
Total receivables	$1,270	$1,573

Significant_Accounting_Policie7

Significant Accounting Policies - Summary of Revenues (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Investment Holdings [Line Items]	'	'
Royalty revenue	$1,821	$1,924
Collaborative and other research and development revenues:	'	'
Collaborative and other research and development	1,637	1,630
Total revenues	3,458	3,554
U.S. Department of Health and Human Services [Member]	'	'
Collaborative and other research and development revenues:	'	'
Collaborative and other research and development	1,341	1,334
Shionogi & Co. Ltd [Member]	'	'
Collaborative and other research and development revenues:	'	'
Collaborative and other research and development	$296	$296

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
	Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$1,610	$1,602	'
Number of stock based compensation plan	2	'	'
Unrecognized compensation cost	11,789	'	'
Recognized cost, remainder of 2014	3,406	'	'
Recognized cost, 2015	3,466	'	'
Recognized cost, 2016	2,607	'	'
Recognized cost, 2017	2,141	'	'
Recognized cost, 2018	169	'	'
Compensation expenses for performance-based stock options	0	'	'
Stock option award period	'3 years	'	'
Stock option vesting period	'4 years	'	'
Stock option granting period after granted	'1 year	'	'
Grant date fair value per share	$8.28	$0.88	'
Expected dividend Yield	0	'	'
Remaining common stock shares	98	'	1,082
Maximum [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock option contractual terms	'10 years	'	'
Minimum [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock option contractual terms	'5 years	'	'
Employee Stock Option [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock option awards granted in percentage	50.00%	'	'
Performance Based Stock Option [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Performance based stock options	1,032	'	'
Stock-based compensation expense	0	'	'
Incentive Plan [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	1,558	1,576	'
Stock option awards granted to nonemployee director vesting period description	'Stock option awards granted to non-employee directors of the Company generally vest monthly over one year.	'	'
Stock option vesting period	'2 years	'	'
Incentive Plan [Member] | Employee Stock Option [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock option awards granted in percentage	25.00%	'	'
ESPP [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$52	$26	'
Common stock shares reserved	975	'	'
Remaining common stock shares	59	'	'
Percentage of salary to purchase common stock	15.00%	'	'
Percentage of common stock shares Beginning	85.00%	'	'
Percentage of common stock shares Ending	85.00%	'	'
Purchase of common stock shares	3	'	'
Maximum number of shares per employee amount	$25	'	'
Purchase intervals	'6 months	'	'
Common stock purchased under ESPP	28	'	'

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Related Activity under Incentive Plan (Detail) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Awards Available, Beginning balance	1,082
Restricted stock awards granted, Awards Available	-593
Restricted stock awards cancelled, Awards Available	'
Stock option awards granted, Awards Available	-391
Stock option awards exercised, Awards Available	'
Stock option awards cancelled, Awards Available	'
Awards Available, Ending balance	98
Options Outstanding, Beginning balance	8,986
Restricted stock awards granted, Options Outstanding	'
Restricted stock awards cancelled, Options Outstanding	'
Stock option awards granted, Options Outstanding	391
Stock option awards exercised, Options Outstanding	-832
Stock option awards cancelled, Options Outstanding	'
Options Outstanding, Ending balance	8,545
Weighted Average Exercise Price, Beginning balance	$4.99
Restricted stock awards granted, Weighted Average Exercise Price	'
Restricted stock awards cancelled, Weighted Average Exercise Price	'
Stock option awards granted, Weighted Average Exercise Price	$10.79
Stock option awards exercised, Weighted Average Exercise Price	$5.18
Stock option awards cancelled, Weighted Average Exercise Price	'
Weighted Average Exercise Price, Ending balance	$5.24

StockBased_Compensation_Weight

Stock-Based Compensation - Weighted Average Assumptions for Stock Option Awards Granted to Employees and Directors under the Incentive Plan (Detail)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'
Expected Life in Years	'5 years 6 months	'4 years 7 months 6 days
Expected Volatility	87.00%	83.00%
Expected Dividend Yield	0.00%	0.00%
Risk-Free Interest Rate	1.60%	0.60%

Collaborative_and_Other_Resear1

Collaborative and Other Research and Development Contracts - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended	0 Months Ended	1 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	Nov. 17, 2011	31-May-10	Mar. 31, 2014	Feb. 24, 2011	Sep. 30, 2009	Jan. 31, 2007	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2014	31-May-10	Mar. 31, 2014
			UAB [Member]	U.S. Department of Health and Human Services [Member]	U.S. Department of Health and Human Services [Member]	U.S. Department of Health and Human Services [Member]	U.S. Department of Health and Human Services [Member]	National Institute of Allergy and Infectious Diseases [Member]	National Institute of Allergy and Infectious Diseases [Member]	AECOM and IRL [Member]	AECOM and IRL [Member]
			Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Collaborative agreement contract value	'	'	'	'	'	$102,661,000	'	'	'	'	'
Collaborative agreement additional contract value	'	'	'	55,000,000	77,191,000	'	'	'	'	'	'
Collaborative agreement adjusted contract value	'	'	'	'	'	'	234,852,000	'	'	'	'
Collaborative agreement expiration date	'	'	'	'	'	'	31-May-14	'	'	'	'
Collaborative agreement initial payment	'	'	'	'	'	'	'	5,000,000	'	'	'
Collaborative agreement contract value	'	'	'	'	'	'	'	22,000,000	'	'	'
Collaborative agreement period of agreement	'	'	'	'	'	'	'	'5 years	'	'	'
Collaborative agreement exercised options awarded	'	'	'	'	'	'	'	'	7,500,000	'	'
Milestone payment minimum	'	'	'	'	'	'	'	'	'	'	1,400,000
Milestone payment maximum	'	'	'	'	'	'	'	'	'	'	4,000,000
Annual license fees minimum	'	'	'	'	'	'	'	'	'	'	150,000
Annual license fees maximum	'	'	'	'	'	'	'	'	'	'	500,000
Advance notice period for termination of agreement	'	'	'	'	'	'	'	'	'	'	'60 days
Reduction in the percentage of future payments	'	0.5	'	'	'	'	'	'	'	'	'
Stock issued during period value for modification of license agreement	'	'	'	'	'	'	'	'	'	5,911,000	'
Payments for modification of license agreement	'	'	'	'	'	'	'	'	'	$90,000	'
Royalty reduction percentage of net proceeds	0.5	'	'	'	'	'	'	'	'	'	'
Number of agreements	'	'	2	'	'	'	'	'	'	'	'
Period of agreement	'	'	'25 years	'	'	'	'	'	'	'	'
Renewable period of agreement	'	'	'5 years	'	'	'	'	'	'	'	'

Royalty_Monetization_Additiona

Royalty Monetization - Additional Information (Detail)	3 Months Ended				3 Months Ended			0 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013	Mar. 31, 2014	Sep. 30, 2013	Mar. 09, 2011	Mar. 09, 2011
	USD ($)	JPY (¥)	USD ($)	USD ($)	PhaRMA Notes [Member]	PhaRMA Notes [Member]	PhaRMA Notes [Member]	JPR Royalty Sub LLC [Member]
					USD ($)	USD ($)	USD ($)	USD ($)
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'
Proceeds from non-recourse notes	'	'	'	'	'	'	'	$30,000,000
Net proceeds from transaction	'	'	'	'	'	'	'	22,691,000
Aggregate principal amount	'	'	'	'	'	'	30,000,000	'
Percentage of interest on notes secured	'	'	'	'	'	'	14.00%	'
Pharma Notes Interest payment date of first payment	1-Sep-11	1-Sep-11	'	'	'	'	'	'
Royalty payments received	'	'	'	'	446,000	1,844,000	'	'
Interest shortfall	'	'	'	2,356,000	'	'	'	'
Aggregate fair value of PhaRMA Notes	'	'	'	'	30,000,000	'	'	'
Percentage of principal balance	'	'	'	'	100.00%	'	'	'
Yen rate per dollar	'	100	'	'	'	'	'	'
Currency hedge premium payable period range one	'2014	'2014	'	'	'	'	'	'
Currency hedge premium payable period range two	'2020	'2020	'	'	'	'	'	'
Payment of premium	0	'	'	'	'	'	'	'
Minimum currency value required for payment of premium on specified date	'	100	'	'	'	'	'	'
Cumulative mark-to-market adjustments - Gain/loss	-1,526,000	'	1,957,000	'	'	'	'	'
Currency Hedge Agreement	1,530,000	'	'	'	'	'	'	'
Currency hedge agreement termination period range one	'2016	'2016	'	'	'	'	'	'
Currency hedge agreement termination period range two	'2020	'2020	'	'	'	'	'	'
Termination fee	1,950,000	'	'	'	'	'	'	'
Termination maximum obligation	5,850,000	'	'	'	'	'	'	'
Maximum amount of hedge collateral	$13,650,000	'	'	'	'	'	'	'

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Aug. 31, 2013	Jun. 30, 2011	Mar. 31, 2014	Dec. 31, 2013	Jul. 13, 2011
Stockholder Equity [Line Items]	'	'	'	'	'
Issue of common stock	'	$70,000	$601	$591	'
Commission rate	'	2.00%	'	'	'
Common stock were issued and sales at market price	'	'	'	'	70,000
Average price per share	'	'	$1.37	'	'
Net proceeds under the agreement	'	'	360	'	'
Selling of company aggregate shares of common stock	'	'	60,065	59,092	'
Public offering of common stock	4,600	'	'	'	'
Public offering of common stock, per share price	$4.40	'	'	'	'
Underwriters' over-allotment allocation on public offering	600	'	'	'	'
Expected net proceeds from common stock	$18,500	'	'	'	'
ATM Agreement [Member]	'	'	'	'	'
Stockholder Equity [Line Items]	'	'	'	'	'
Selling of company aggregate shares of common stock	'	'	301	'	'