XenoPort (XNPT) 10-K 28 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 14, 2014	Jun. 28, 2013
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Trading Symbol	'XNPT	'	'
Entity Registrant Name	'XENOPORT INC	'	'
Entity Central Index Key	'0001130591	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Filer Category	'Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	60,004,125	'
Entity Public Float	'	'	$228,100,000

BALANCE_SHEETS

BALANCE SHEETS (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$20,584	$36,134
Short-term investments	38,074	102,868
Accounts receivable	939	'
Right to the HORIZANT business	'	13,557
Inventories	1,262	'
Prepaids and other current assets	2,826	2,529
Total current assets	63,685	155,088
Property and equipment, net	2,552	1,528
Long-term inventories	10,185	'
Restricted investments and other assets	2,119	2,432
Total assets	78,541	159,048
Current liabilities:	'	'
Accounts payable	1,432	567
Accrued compensation	2,741	4,875
Accrued restructuring charges	'	993
Accrued preclinical and clinical costs	824	4,397
Other accrued liabilities	3,938	1,424
Deferred revenue	1,134	1,515
Total current liabilities	10,069	13,771
Deferred revenue	11,997	12,753
Other noncurrent liability	2,782	2,314
Commitments and contingencies	'	'
Stockholders' equity:	'	'
Preferred stock, $0.001 par value; 5,000 shares authorized; no shares issued or outstanding	'	'
Common stock, $0.001 par value; 100,000 shares authorized; 47,800 and 47,068 shares issued and outstanding, at December 31, 2013 and 2012, respectively	48	47
Additional paid-in capital	591,128	581,741
Accumulated other comprehensive income	'	22
Accumulated deficit	-537,483	-451,600
Total stockholders' equity	53,693	130,210
Total liabilities and stockholders' equity	$78,541	$159,048

BALANCE_SHEETS_Parenthetical

BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Per Share data, unless otherwise specified
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	$0.00	$0.00
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	47,800	47,068
Common stock, shares outstanding	47,800	47,068

STATEMENTS_OF_COMPREHENSIVE_LO

STATEMENTS OF COMPREHENSIVE LOSS (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:	'	'	'
Product sales, net	$6,414	'	'
Collaboration revenue	1,137	11,515	8,515
Royalty revenue	400	109	'
Net revenue from unconsolidated joint operating activities	'	10,000	35,000
Total revenues	7,951	21,624	43,515
Operating expenses:	'	'	'
Cost of product sales	1,170	'	'
Research and development	33,325	42,947	43,788
Selling, general and administrative	59,084	30,244	30,427
Gain on litigation settlement	'	-20,499	'
Restructuring charges	'	'	2,923
Total operating expenses	93,579	52,692	77,138
Loss from operations	-85,628	-31,068	-33,623
Interest income	213	254	243
Interest expense	-468	'	'
Net loss	-85,883	-30,814	-33,380
Other comprehensive loss:	'	'	'
Unrealized gains (losses) on available-for-sale securities	-22	38	-10
Comprehensive loss	($85,905)	($30,776)	($33,390)
Basic and diluted net loss per share	($1.81)	($0.78)	($0.94)
Shares used to compute basic and diluted net loss per share	47,545	39,434	35,400

STATEMENTS_OF_STOCKHOLDERS_EQU

STATEMENTS OF STOCKHOLDERS' EQUITY (USD $)	Total	Glaxo Group Limited	Common Stock	Common Stock	Additional Paid-In Capital	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
In Thousands, except Share data				Glaxo Group Limited		Glaxo Group Limited
Beginning Balance at Dec. 31, 2010	$93,959	'	$35	'	$481,336	'	($6)	($387,406)
Beginning Balance (in shares) at Dec. 31, 2010	'	'	35,226,762	'	'	'	'	'
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)	'	'	143,969	'	'	'	'	'
Issuance of common stock upon exercise of options and vesting of restricted stock units	-624	'	'	'	-624	'	'	'
Issuance of common stock in connection with Employee Stock Purchase Plan (in shares)	'	'	143,905	'	'	'	'	'
Issuance of common stock in connection with Employee Stock Purchase Plan	802	'	'	'	802	'	'	'
Employee stock-based compensation expense	14,388	'	'	'	14,388	'	'	'
Change in unrealized gains (losses) on investments	-10	'	'	'	'	'	-10	'
Net loss	-33,380	'	'	'	'	'	'	-33,380
Ending Balance at Dec. 31, 2011	75,135	'	35	'	495,902	'	-16	-420,786
Ending Balance (in shares) at Dec. 31, 2011	'	'	35,514,636	'	'	'	'	'
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)	'	'	259,650	'	'	'	'	'
Issuance of common stock upon exercise of options and vesting of restricted stock units	-480	'	1	'	-481	'	'	'
Issuance of common stock in connection with Employee Stock Purchase Plan (in shares)	'	'	185,249	'	'	'	'	'
Issuance of common stock in connection with Employee Stock Purchase Plan	763	'	'	'	763	'	'	'
Employee stock-based compensation expense	12,281	'	'	'	12,281	'	'	'
Issuance of common stock (in shares)	'	'	7,076,922	4,031,212	'	'	'	'
Issuance of common stock	43,019	30,268	7	4	43,012	30,264	'	'
Change in unrealized gains (losses) on investments	38	'	'	'	'	'	38	'
Net loss	-30,814	'	'	'	'	'	'	-30,814
Ending Balance at Dec. 31, 2012	130,210	'	47	'	581,741	'	22	-451,600
Ending Balance (in shares) at Dec. 31, 2012	47,068,000	'	47,067,669	'	'	'	'	'
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)	'	'	590,242	'	'	'	'	'
Issuance of common stock upon exercise of options and vesting of restricted stock units	-1,875	'	1	'	-1,876	'	'	'
Issuance of common stock in connection with Employee Stock Purchase Plan (in shares)	'	'	142,455	'	'	'	'	'
Issuance of common stock in connection with Employee Stock Purchase Plan	719	'	'	'	719	'	'	'
Employee stock-based compensation expense	10,544	'	'	'	10,544	'	'	'
Change in unrealized gains (losses) on investments	-22	'	'	'	'	'	-22	'
Net loss	-85,883	'	'	'	'	'	'	-85,883
Ending Balance at Dec. 31, 2013	$53,693	'	$48	'	$591,128	'	'	($537,483)
Ending Balance (in shares) at Dec. 31, 2013	47,800,000	'	47,800,366	'	'	'	'	'

STATEMENTS_OF_CASH_FLOWS

STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities	'	'	'
Net loss	($85,883)	($30,814)	($33,380)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Depreciation and amortization	1,199	2,516	3,513
Accretion of investment discounts and amortization of investment premiums, net	1,007	1,295	677
Stock-based compensation expense	10,544	12,281	14,388
Gain on litigation settlement, net of stock premium in connection with the stock purchase agreement with GSK	'	-11,243	'
Changes in assets and liabilities:	'	'	'
Accounts receivable	-939	'	'
Prepaids and other current and noncurrent assets	16	712	-248
Inventories	286	'	'
Accounts payable	865	-465	517
Accrued compensation	-2,134	699	1,683
Accrued restructuring charges	-993	-1,737	2,730
Accrued preclinical and clinical costs	-3,573	-36	-451
Other accrued liabilities, current and noncurrent	2,839	677	-1,333
Deferred revenue, current and noncurrent	-1,137	-1,515	-1,515
Net cash used in operating activities	-77,903	-27,630	-13,419
Investing activities	'	'	'
Purchases of investments	-91,000	-147,645	-141,357
Proceeds from maturities of investments	154,765	112,576	157,017
Purchases of property and equipment	-256	-123	-225
Net cash provided by (used in) investing activities	63,509	-35,192	15,435
Financing activities	'	'	'
Net cash proceeds provided by (used in) issuance of common stock and exercise of stock options	-1,156	43,302	178
Proceeds from issuance of common stock to GSK in connection with the stock purchase agreement	'	30,268	'
Net cash provided by (used in) financing activities	-1,156	73,570	178
Net increase (decrease) in cash and cash equivalents	-15,550	10,748	2,194
Cash and cash equivalents at beginning of period	36,134	25,386	23,192
Cash and cash equivalents at end of period	20,584	36,134	25,386
Non-cash investing activity	'	'	'
Right to the HORIZANT business	'	13,557	'
Inventories	11,733	'	'
Manufacturing property and equipment	$1,967	'	'

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Organization and Summary of Significant Accounting Policies	'
	1	Organization and Summary of Significant Accounting Policies
	Nature of Operations
	XenoPort, Inc., or the Company, was incorporated in the state of Delaware on May 19, 1999. The Company is a biopharmaceutical company focused on developing and commercializing a portfolio of internally discovered product candidates for the potential treatment of neurological and other disorders. The Company is currently commercializing HORIZANT® (gabapentin enacarbil) Extended-Release Tablets in the United States and is developing its novel fumaric acid ester product candidate, XP23829, as a potential treatment for psoriasis and/or relapsing forms of multiple sclerosis, or MS. The Company’s pipeline of product candidates also includes potential treatments for patients with spasticity related to spinal cord injury and Parkinson’s disease. HORIZANT and the Company’s product candidates are prodrugs that are typically created by modifying the chemical structure of currently marketed drugs, referred to as parent drugs, and are designed to correct limitations in the oral absorption, distribution and/or metabolism of the parent drug. HORIZANT and each of the Company’s product candidates are orally-available, patented molecules that address potential markets with clear unmet medical needs. The Company’s facilities are located in Santa Clara, California.
	On November 8, 2012, the Company reached an agreement with Glaxo Group Limited, or GSK, to terminate the Amended and Restated Development and Commercialization Agreement dated November 7, 2010, between the Company and GSK regarding HORIZANT.
	Under the terms of the November 2012 termination and transition agreement, during a transition period that ended on April 30, 2013, GSK continued to exclusively commercialize, promote, manufacture and distribute HORIZANT in the United States. The Company was not eligible to receive any milestone payments from GSK and did not receive any revenue or incur any losses from GSK’s sales of HORIZANT during the transition period. GSK continued to fully fund the costs associated with the management and conduct of required post-marketing clinical studies initiated by GSK prior to the date of the termination and transition agreement. In addition, GSK provided to the Company inventory of gabapentin enacarbil in GSK’s possession that was not required for use by GSK in the manufacture of HORIZANT and related manufacturing property and equipment. In exchange for such inventory, the Company will make annual payments to GSK of $1,000,000 for six years beginning in 2016, which was recorded at its present value as “Other noncurrent liability” on the Company’s balance sheet for the periods ended December 31, 2013 and December 31, 2012 and is being accreted to its contractual value over the repayment period. Pursuant to a separate stock purchase agreement, or SPA, entered into between the Company and GSK on November 8, 2012, GSK purchased $20,000,000 of the Company’s common stock, or an aggregate of 1,841,112 shares at $10.863 per share, which per share price represented a 12.5 percent premium to the average of the closing prices of the Company’s common stock for the ten trading days prior to October 31, 2012. In addition, on November 9, 2012, the Company exercised a put option requiring GSK to purchase an additional 2,190,100 shares of the Company’s common stock at $9.132 per share, which per share price represented a 12.5 percent premium to the average of the closing prices of the Company’s common stock for the ten trading days prior to November 9, 2012. On May 1, 2013, the Company completed the acquisition of the HORIZANT business in accordance with the termination and transition agreement and assumed all responsibilities and associated rights for the further development, manufacturing and commercialization of HORIZANT in the United States on that date. GSK was responsible for the commercial manufacture and supply of HORIZANT during the transition period. GSK also supplied the Company with HORIZANT following the end of the transition period through October 2013 and also performed certain validation work with respect to the 300 mg dosage form of HORIZANT and other services for the Company through December 2013. The Company did not assume any liabilities of GSK’s HORIZANT business as of the acquisition date. This termination and transition agreement between the Company and GSK also provided for a mutual release of claims and resolved all ongoing litigation between the parties.
	Basis of Preparation
	The Company’s financial statements are prepared in accordance with the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or the Codification, which is the single source of authoritative U.S. generally accepted accounting principles, or GAAP.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates.
	Fair Value of Financial Instruments
	The carrying amounts of certain of the Company’s financial instruments, including cash and cash equivalents and short-term investments, restricted investments, accounts receivables and accounts payable, approximate their fair value due to their short-term maturities. The Company accounts for the fair value of its financial instruments in accordance with the provisions of the Fair Value Measurement topic of the Codification.
	Fair value is the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The Company applies the market approach valuation technique for fair value measurements on a recurring basis and attempts to maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. All of the Company’s cash equivalents and short-term investments are measured using inputs classified at Level 1 or Level 2 within the fair value hierarchy. Level 1 inputs are quoted prices in active markets for identical assets. Level 2 inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Level 3 inputs are unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes and market reference data.
	Cash Equivalents and Short-Term Investments
	The Company considers all highly liquid investments with original maturities of 90 days or less at the time of purchase to be cash equivalents, which primarily consist of money market funds, U.S. government-sponsored agencies and corporate debt securities.
	Management determines the appropriate classification of securities at the time of purchase. All investments have been designated as available-for-sale. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company has classified all investments as short-term, even though the stated maturity may be one year or more beyond the current balance sheet date. Available-for-sale securities are carried at estimated fair value with unrealized gains and losses reported as a component of other comprehensive loss in the statements of comprehensive loss.
	The cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities, if any, are recorded in interest income and expense. The cost of securities sold is based on the specific-identification method. Interest and dividends are included in interest income.
	Restricted Investments
	Under a facilities operating lease agreement, the Company is required to secure a letter of credit with cash or securities. At December 31, 2013 and 2012, the Company recorded $1,500,000 and $1,705,000, respectively, of restricted investments related to the letter of credit (see Note 8 for more information).
	In connection with the Company’s license to use radioactive materials in its research facilities, it must maintain a $225,000 letter of credit with the Radiological Health Branch of the State of California. This requirement has been fulfilled through certificates of deposit with a financial institution. The fair value of the secured amount of $225,000 and $250,000 was classified as restricted investments in the accompanying balance sheets at both December 31, 2013 and 2012.
	Segment Information
	The Company operates in one operating segment, which is the development and commercialization of product candidates for the potential treatment of neurological and other disorders, and has operations solely in the United States. To date, all of the Company’s revenues from product sales are related to sales of HORIZANT in the United States. The Company has recognized up-front license payment and royalty revenue under its collaboration agreement with Astellas Pharma Inc. (see Note 2 for more information on the collaboration agreement).
	Concentrations of Risk
	The Company invests cash that is not being used for operational purposes. This exposes the Company to credit risk in the event of default by the institutions holding the cash and cash equivalents and available-for-sale securities. The credit risk is mitigated by the Company’s investment policy, which allows for the purchase of low risk debt securities issued by the U.S. government, U.S. government-sponsored agencies and highly rated banks and corporations, subject to certain concentration limits. The maturities of these securities are maintained at no longer than 18 months. The Company believes its established guidelines for investment of its excess cash enhances safety and liquidity through its policies on diversification and investment maturity.
	Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and available-for-sale investment securities in high-credit quality debt securities issued by the U.S. government, U.S. government-sponsored enterprises and highly rated banks and corporations. The carrying amounts of cash equivalents and available-for-sale investment securities are stated at fair value.
	The Company is subject to credit risk from its accounts receivable related to product sales. The Company’s trade accounts receivable arises from product sales in the United States. Three wholesale distributors represented 47%, 33% and 16% of product sales for the year ended December 31, 2013. These three customers individually comprised 45%, 29% and 22%, respectively, of product sales related to accounts receivable as of December 31, 2013. Accounts receivable balances related to product sales were $939,000 for the year ended December 31, 2013. The Company did not have product sales and accounts receivable as of December 31, 2012. To date, the Company has not experienced any losses with respect to the collection of its accounts receivable and believes that its accounts receivable are collectible.
	The Company relies on a single third-party contract manufacturer organization to manufacture HORIZANT.
	Property and Equipment
	Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, which is generally five to ten years for the Company’s laboratory equipment, furniture and fixtures and manufacturing property and equipment and generally three years for the Company’s computer equipment and software. Leasehold improvements are amortized over their estimated useful lives or the remaining lease term, whichever is shorter.
	Revenue Recognition
	Product Sales
	The Company began selling HORIZANT to wholesalers in May 2013 following the return of the Company’s commercial rights from GSK. The Company recognizes revenue from HORIZANT product sales when there is persuasive evidence that an arrangement exists, delivery to the customer has occurred, the price is fixed or determinable and collectability is reasonably assured. Revenue from product sales is recorded net of estimated allowances for customer incentives such as cash discounts for prompt payment, distributor fees, expected returns, as appropriate (which are based on an analysis of historical return rates and deductions of HORIZANT, since its commercial launch by GSK in the second quarter of 2011), government rebates such as Medicaid reimbursements and patient assistance programs. Calculating certain of these items involves estimates and judgments based on contractual terms, historical utilization rates data for HORIZANT and new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future utilization rates for these programs and channel inventory data. If future actual results vary from the Company’s estimates, the Company may need to adjust these estimates, which could have an effect on product sales and earnings in the period of adjustment.
	Items Deducted from Gross Product Sales
	Prompt Pay Discount
	The Company offers cash discounts to its customers, generally 2% of the sales price, as an incentive for prompt payment. Based on GSK’s commercialization experience, the Company expects customers to continue to comply with the prompt payment terms to earn the cash discount as the Company is selling HORIZANT to the same customers under similar prompt payment terms and conditions. The Company estimates cash discounts for prompt payment based on contractual terms, GSK’s historical customer utilization rates and the Company’s historical customer utilization rates. The Company accounts for cash discounts by reducing accounts receivable by the full amount and recognizing the discount as a reduction of revenue in the same period the related revenue is recognized.
	Distributor Fees
	Under the Company’s inventory management agreements with significant wholesalers, the Company pays the wholesalers a fee primarily for distribution services as well as the maintenance of inventory levels. These distributor fees are based on a contractually determined fixed percentage of sales. The Company accrues the contractual amount and recognizes the discount as a reduction of revenue in the same period the related revenue is recognized.
	Product Returns
	The Company does not provide its customers with a general right of product return, but permits returns if the product is damaged or defective when received by the customer, or if the product has or is nearly expired. HORIZANT tablets currently have a shelf-life of 36 months from the date of manufacture. The Company will accept returns for products that will expire within six months or that have expired up to one year after their expiration dates. The Company obtained actual return history by type from GSK since GSK’s product launch in 2011, which provides a basis to reasonably estimate the Company’s future product returns. The Company estimates returns taking into consideration Company-specific adjustments to GSK’s returns history, the shelf life of product, shipment and prescription trends and estimated distribution channel inventory levels.
	Government Rebates and Chargebacks
	The Company participates in a number of government rebate programs, such as the Medicaid Drug Rebate Program that provides assistance to eligible low-income patients based on each individual state’s guidelines regarding eligibility and services, Public Health Services or 340b programs, and the Medicare Part D Coverage Gap Discount Program, which provides rebates on prescriptions that fall within the “donut hole” coverage gap; and the Department of Veterans Affairs that offers discounts to authorized users of HORIZANT. HORIZANT is also listed on the Federal Supply Schedule, or FSS, of the General Services Administration which provides a discount to the Department of Defense, Department of Veterans Affairs, and TriCare. The Company estimates reductions to the Company’s revenues for government rebate programs based on product pricing, current rebates, GSK’s historical utilization rates, the Company’s actual utilization rates, new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future rebates for these programs and estimated levels of inventory in the distribution channel.
	Patient Assistance
	The Company offers a co-pay card program to assist commercially insured patients with the cost of their HORIZANT related co-payments. Participating retail pharmacies get reimbursed by the Company for the amount of the co-pay assistance provided to eligible patients. The Company estimates and accrues the cost of the co-pay program based on historical redemption activity for this program. The Company reimburses the participating pharmacies approximately one month after the prescriptions subject to co-pay assistance are filled.
	Multiple-Element Arrangements
	Revenue arrangements are accounted for in accordance with the provisions of the Revenue Recognition-Multiple-Element Arrangements topic of the Codification.
	In evaluating arrangements with multiple elements, the Company considers whether components of the arrangement represent separate units of accounting based upon whether certain criteria are met, including whether the delivered element has stand-alone value to the customer and whether there is objective and reliable evidence of the fair value of the undelivered items. This evaluation requires subjective determinations and requires management to make judgments about the fair value of individual elements and whether such elements are separable from other aspects of the contractual relationship. The consideration received in such arrangements is allocated among the separate units of accounting based on the relative selling price method under which the selling price for each deliverable is determined using vendor-specific objective evidence of selling price, if it exists; otherwise, third-party evidence of selling price. If vendor-specific objective evidence and third-party evidence of selling price are not available for a deliverable, the Company will use its best estimate of the selling price for that deliverable when applying the relative selling price method. The applicable revenue recognition criteria are applied to each of the separate units.
	Revenues from multiple deliverables combined as a single unit of accounting are deferred and recognized over the period during which the Company remains obligated to perform services. The specific methodology for the recognition of the revenue (e.g., straight-line or according to specific performance criteria) is determined on a case-by-case basis according to the facts and circumstances applicable to a given agreement.
	Payments received in excess of revenues recognized are recorded as deferred revenue until such time as the revenue recognition criteria have been met.
	Collaboration revenue includes revenue from the Company’s current collaboration agreement with Astellas Pharma Inc. Net revenue from unconsolidated joint operating activities included all revenue that resulted solely from the Company’s terminated collaboration agreement with GSK. The Company accounts for the revenue-related activities of these collaboration agreements as follows:
		•		Up-front, licensing-type payments. Up-front, licensing-type payments are assessed to determine whether or not the licensee is able to obtain any stand-alone value from the license. Where this is not the case, the Company does not consider the license deliverable to be a separate unit of accounting, and the revenue is deferred with revenue recognition for the license fee being assessed in conjunction with the other deliverables that constitute the combined unit of accounting.
		•		Milestones. Revenue recognition will occur only if the consideration earned from the achievement of a milestone meets all the criteria for the milestone to be considered substantive at the inception of the arrangement, such that it: (i) is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company’s performance to achieve the milestone; (ii) relates solely to past performance; and (iii) is reasonable relative to all deliverables and payment terms in the arrangement.
	The Company will assess the nature of contingent payments, and appropriate accounting for, these payments on a case-by-case basis in accordance with the provisions of the Revenue Recognition topic of the Codification.
		•		Profit and loss sharing. This represented the Company’s share of the profits and losses from the co-promotion of HORIZANT with GSK under the terminated collaboration with GSK. Amounts were recognized in the period in which the related activities occurred, and their financial statement classification was based on the Company’s assessment that these activities constituted part of the Company’s ongoing central operations.
		•		Product royalties. The Company is entitled to receive royalties on net sales of gabapentin enacarbil (known as REGNITE) in Japan. Astellas initiated sales of REGNITE in Japan in July 2012, and the Company recognizes the associated product royalties when they can be reliably measured and collectability is reasonably assured (generally upon receipt of the royalty payment).
	Cost of Product Sales
	Cost of product sales includes direct and indirect costs to manufacture product sold, including tableting, packaging, storage, shipping and handling costs and inventory write-downs, if any.
	Accounts Receivable
	Trade accounts receivable are recorded net of allowances for cash discounts for prompt payment, wholesaler discounts and chargebacks. The need for bad debt allowance is evaluated each reporting period based on the Company’s assessment of the credit worthiness of its customers.
	Inventories
	Inventories are stated at the lower of cost or market. Cost is determined on a first-in, first-out, or FIFO, basis. The Company regularly evaluates the Company’s inventories for excess quantities and obsolescence (expiration), taking into account such factors as historical and anticipated future sales compared to quantities on hand and the remaining shelf life of HORIZANT. Write-downs of inventories are considered to be permanent reductions in the cost basis of inventories.
	Inventories that are not expected to be consumed within 12 months following the balance sheet date are classified as long-term inventories.
	Inventories as of December 31, 2013 were summarized as follows (in thousands):
	Raw materials		$	10,258
	Work in progress			76
Finished goods			1,113
Total inventory			11,447
Less: Long-term inventories			10,185
Total inventory classified as current		$	1,262
Long-term inventories consist of Active Pharmaceutical Ingredient, or API, of gabapentin enacarbil used for production of the Company’s product HORIZANT. The Company evaluates demand for HORIZANT and expected consumption of the API based on long-term projected sales of HORIZANT.
The Company did not have inventories as of December 31, 2012.
Research and Development
All research and development costs, including those funded by third parties, are expensed as incurred. Research and development costs consist of salaries, employee benefits, laboratory supplies, costs associated with clinical trials, including amounts paid to clinical research organizations, other professional services and facility costs.
Clinical Trials
The Company accrues and expenses the costs for clinical trial activities performed by third parties based upon estimates of the percentage of work completed over the life of the individual study in accordance with agreements established with contract research organizations and clinical trial sites. The Company determines the estimates through discussions with internal clinical personnel and external service providers as to progress or stage of completion of trials or services and the agreed upon fee to be paid for such services. Costs of setting up clinical trial sites for participation in the trials are expensed immediately as research and development expenses. Clinical trial site costs related to patient visits are accrued as patients progress through the trial and are reduced by any payments made to the clinical trial site. Non-refundable advance payments for research and development goods or services are recognized as expense as the related goods are delivered or the related services are provided in accordance with the provisions of the Research and Development Arrangements topic of the Codification.
Nonretirement Postemployment Benefits
On May 31, 2012, the Company adopted the XenoPort Amended and Restated 2012 Severance Plan, or the 2012 Severance Plan, for the benefit of the Company’s non-executive employees. Under the terms of the 2012 Severance Plan, a non-executive employee terminated by the Company because of elimination of his or her position is eligible to receive continuation of medical insurance under COBRA and specified severance payments based on the employee’s level and years of service with the Company. The Company accounts for employee termination benefits in accordance with the provisions of the Compensation-Nonretirement Postemployment Benefits topic of the Codification and records employee termination liabilities once they are both probable and estimable for severance provided under the Company’s existing severance program.
On June 14, 2013, the Company implemented a reduction in force that included the elimination of certain non-executive positions as the Company completed certain work projects on its arbaclofen placarbil development program. As a result, the Company recorded severance benefits charges of $703,000 in 2013, which were included in the “Research and development” line of the “Operating expenses” section of the Company’s statements of comprehensive loss. As of December 31, 2013, there was no associated liability balance.
Stock-Based Compensation
The Compensation — Stock Compensation topic of the Codification establishes accounting for stock-based awards exchanged for employee services. In accordance with this topic, for stock options, awards and stock purchase rights under the Company’s employee stock purchase plan, or ESPP, stock-based compensation cost is measured at grant date, based on the fair value of the award, and is recognized as expense over the requisite employee service period.
The effect of recording stock-based compensation under the Compensation — Stock Compensation topic was as follows:
		Year Ended December 31,
		2013			2012			2011
		(In thousands, except
		per share amounts)
Stock-based compensation by type of award:
Employee stock options and awards		$	10,083		$	11,956		$	14,044
ESPP			461			325			344
Total stock-based compensation		$	10,544		$	12,281		$	14,388
Effect on basic and diluted net loss per share		$	(0.22	)	$	(0.31	)	$	(0.41	)
The Company’s employee non-cash stock-based compensation was reported as follows:
		Year Ended December 31,
		2013			2012			2011
		(In thousands)
Research and development		$	3,059		$	4,364		$	5,208
Selling, general and administrative			7,485			7,917			9,180
		$	10,544		$	12,281		$	14,388
Valuation Assumptions
The Company estimates the fair value of all of its stock options and stock purchase rights on the date of grant using a Black-Scholes valuation model that requires the input of highly subjective assumptions, including the option’s expected life and the price volatility of the underlying stock. The Company derived the expected life assumptions using data obtained from similar entities, taking into consideration factors such as industry, stage of life cycle, size and financial leverage. The Company has determined that its historical volatility can be used to derive the expected stock price volatility assumption. The Company expenses the resulting charge using the straight-line attribution method over the vesting period. Restricted stock units are measured at the fair value of the Company’s common stock on the date of grant and expensed over the period of vesting using the straight-line attribution approach. The calculation of the Black-Scholes valuations used the following weighted-average assumptions:
		Year Ended December 31,
		2013		2012	2011
Dividend yield		0%		0%	0%
Volatility for options		0.82		0.81	0.77
Volatility for ESPP		0.59		0.65	0.73
Weighted-average expected life of options (years)		5.25		5.09	5.34
Weighted-average expected life of ESPP rights (years)		0.5		0.5	0.5
Risk-free interest rate for options		0.70-1.60%		0.62-1.02%	0.90-2.26%
Risk-free interest rate for ESPP rights		0.07-0.17%		0.07-0.27%	0.07-0.19%
The Black-Scholes option-pricing model was developed for use in estimating the fair value of short-lived, exchange-traded options that have no vesting restrictions and are fully transferable.
Income Taxes
Income taxes are accounted for in accordance with the Income Taxes topic of the Codification using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is more-likely-than-not that the deferred tax assets will not be realized.
The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at the reporting date.
As of December 31, 2013, the Company had unrecognized tax benefits and expects no significant changes in unrecognized tax benefits in the next 12 months (see Note 11 for more information).
The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense. To date, there have been no interest or penalties charged to the Company in relation to the underpayment of income taxes.
Comprehensive Loss
The Company presents all non-owner changes in stockholders’ equity in a single continuous statement of comprehensive loss and shows: (i) each component of net loss along with total net loss; (ii) each component of other comprehensive loss along with a total for other comprehensive loss; and (iii) a total amount for comprehensive loss. The Company’s other comprehensive loss is comprised of unrealized gains (losses) on available-for-sale securities.
Advertising Costs
Advertising costs, included in selling, general and administrative expenses, are charged to expense as incurred. Advertising expenses for the year ended December 31, 2013, was $8,244,000. The Company did not have advertising costs for the years ended December 31, 2012 and 2011.
Net Loss Per Share
Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period without consideration for potential common shares. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period plus any dilutive potential common shares for the period determined using the treasury-stock method. For purposes of this calculation, restricted stock units, options to purchase stock and warrants are considered to be potential common shares and are only included in the calculation of diluted net loss per share when their effect is dilutive.
		Year Ended December 31,
		2013			2012			2011
		(In thousands, except
		per share amounts)
Numerator:
Net loss		$	(85,883	)	$	(30,814	)	$	(33,380	)
Denominator:
Weighted-average common shares outstanding			47,545			39,434			35,400
Basic and diluted net loss per share		$	(1.81	)	$	(0.78	)	$	(0.94	)
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Restricted stock units and options to purchase common stock			6,824			6,339			5,903
Warrants outstanding			283			283			305
			7,107			6,622			6,208
On January 29, 2014, the Company completed an underwritten public offering of 12,000,000 shares of its common stock at a price to the public of $6.00 per share (see Note 14 for more information).

Collaboration_Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2013
Collaboration Agreements	'
	2	Collaboration Agreements
	Astellas Pharma Inc.
	In December 2005, the Company entered into an agreement pursuant to which it licensed to Astellas Pharma Inc., exclusive rights to develop and commercialize gabapentin enacarbil in Japan, Korea, the Philippines, Indonesia, Thailand and Taiwan. Astellas commenced commercialization of gabapentin enacarbil in Japan, and began selling gabapentin enacarbil in July 2012 under the trade name of REGNITE® (gabapentin enacarbil) Extended-Release Tablets. In May 2013, Astellas notified the Company that it did not have plans for the commercialization of gabapentin enacarbil in the five other Asian countries in its territory. As a result, in May 2013, the rights to gabapentin enacarbil in Korea, the Philippines, Indonesia, Thailand and Taiwan reverted to the Company. In the year ended December 31, 2013, the Company recognized revenue of $1,137,000 representing amortization of the up-front license payment under this agreement. In the years ended December 31, 2012 and 2011, the Company recognized revenue of $1,515,000, representing amortization of the up-front license payment under this agreement. In the year ended December 31, 2012, the Company also recognized a $10,000,000 milestone payment in connection with the approval of REGNITE in Japan and, for the year ended December 31, 2011, the Company also recognized a $7,000,000 milestone payment in connection with the U.S. Food and Drug Administration, or FDA, approval of gabapentin enacarbil for the treatment of moderate-to-severe primary restless legs syndrome, or RLS, in adults. For the year ended December 31, 2013, the Company recognized $400,000 in royalty revenue. In the three months ended December 31, 2012, the Company recognized $109,000 in royalty revenue based on the third quarter 2012 net sales. As of December 31, 2013, the Company had recognized an aggregate of $52,378,000 of revenue pursuant to this agreement. At December 31, 2013, $13,131,000 of revenue was deferred under this agreement and was being recognized on a straight-line basis over a period that the Company expects to remain obligated to provide services, of which $1,134,000 was classified within current liabilities and the remaining $11,997,000 was recorded as a noncurrent liability.
	Glaxo Group Limited
	Prior to the November 2012 termination and transition agreement (see Note 1 for more information), in January 2012, the Company provided notice to GSK of the Company’s belief that, among other matters, GSK had materially breached its contractual obligation. In February 2012, the Company and GSK commenced litigation. The November 2012 termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the parties (see Note 3 for more information).
	In February 2007, the Company entered into an exclusive collaboration agreement with GSK to develop and commercialize gabapentin enacarbil in all countries of the world excluding the Astellas territory. In November 2010, the Company amended and restated its collaboration agreement with GSK, pursuant to which the Company reacquired all rights to gabapentin enacarbil outside of the United States previously granted to GSK (which excludes the Astellas territory) and obtained the right, but not the obligation, to pursue development of HORIZANT for: (i) the potential treatment of diabetic peripheral neuropathy; (ii) the potential treatment of postherpetic neuralgia, or PHN, to the extent that a product label would reflect a superiority claim over a currently approved drug; and (iii) any additional indications in the United States. In April 2011, the FDA approved HORIZANT for the treatment of RLS in adults. Shipments of HORIZANT to wholesalers commenced in June 2011, and HORIZANT was commercially launched in July 2011. In June 2012, the FDA approved HORIZANT for the management of PHN in adults. Under the collaboration agreement, GSK remained responsible for further development and regulatory matters with respect to HORIZANT and manufacturing and commercialization of HORIZANT in the United States for all indications.
	In March 2007, GSK made an up-front, non-refundable license payment of $75,000,000. Under the terms of the amended and restated collaboration agreement, the Company received $130,000,000 in aggregate clinical and regulatory event-based payments that have been fully recognized through December 31, 2012, including $10,000,000 received and fully recognized in June 2012 in connection with the first commercial sale of HORIZANT for the management of PHN in adults. The Company concluded that the up-front license payment did not have value to GSK on a stand-alone basis without the benefit of the specified development activities that the Company performed in connection with HORIZANT and that $85,000,000 of milestones paid for clinical trial and pre-clinical activities were either not sufficiently substantive or not sufficiently at risk to be accounted for using the “when-earned” model. Accordingly, these milestones and the up-front payment were combined into one unit of accounting that was recognized over the development period to commercialization of the product, during which time delivery of substantially all of the efforts required for the completion of the Company’s contractual responsibilities under the GSK agreement occurred, and the Company determined that no additional performance obligations resulted from the amended agreement. As of December 31, 2012, the Company had recognized an aggregate of $205,000,000 of up-front license, milestone and contingent event-based payments pursuant to this agreement and no revenue was deferred under this agreement.
	The Company’s net revenue from unconsolidated joint operating activities from the GSK collaboration agreement was $0, $10,000,000 and $35,000,000 for the year ended December 31, 2013, 2012 and 2011, respectively.
	The following table presents the Company’s total revenues that have been recognized pursuant to its current collaboration agreement with Astellas and its terminated collaboration agreement with GSK (in thousands):
			Year Ended December 31,
			2013		2012		2011
	Astellas		$	1,537	$	11,624	$	8,515
	GSK			—		10,000		35,000
			$	1,537	$	21,624	$	43,515

Acquisitions_and_AcquisitionRe

Acquisitions and Acquisition-Related Items	12 Months Ended
	Dec. 31, 2013
Acquisitions and Acquisition-Related Items	'
	3	Acquisitions and Acquisition-Related Items
	On November 8, 2012, the Company reached an agreement with GSK to terminate the collaboration agreement dated November 7, 2010 between the Company and GSK (see Note 1 for more information on the termination and transition agreement and see Note 2 for more information on the terminated collaboration agreement).
	Pursuant to a separate stock purchase agreement entered into between the parties on November 8, 2012, GSK purchased $20,000,000 of common stock of the Company, or an aggregate of 1,841,112 shares at $10.863 per share, which per share price represented a 12.5 percent premium to the average of the closing prices of the Company’s common stock for the ten trading days prior to October 31, 2012. In addition, the Company was granted a Put Option that was exercisable for six months from November 9, 2012 to require GSK to purchase up to an additional $20,000,000 of common stock of the Company at a 12.5 percent premium to the average of the closing prices of the Company’s common stock for the ten trading days prior to the day the Company exercises this option. On November 9, 2012, the Company exercised the Put Option in full. The value of the Put Option was the difference between the price paid by GSK for the shares put, $20,000,000, and the value of the shares based on the Company’s closing stock price on the day of exercise. On November 9, 2012, pursuant to the exercise of the Put Option, GSK purchased an additional 2,190,100 shares at $9.132 per share.
	The Company accounted for the termination and transition agreement and the stock purchase agreement with GSK in accordance with the provisions of the Business Combinations topic of the Codification. Under the provisions of the Business Combinations topic, the acquisition date for a business is the date on which the Company obtains control of the acquiree. The Company obtained control of the HORIZANT business at the end of the transition period, or May 1, 2013. Accordingly, on November 8, 2012, the transaction did not meet the definition of a business combination, and the Company accounted for the transaction as a multiple-element arrangement consisting of the settlement of a pre-existing relationship in exchange for the right to acquire the HORIZANT business at the end of a defined transition period, the sale of common stock at a premium and the obligation by the Company to make certain cash payments to GSK in the future. The value of the HORIZANT business was based on an estimated discounted cash flow analysis attributable to the HORIZANT business.
	The following table summarizes the fair value of consideration exchanged as part of the termination and transition agreement (in thousands):
	Cash payable to GSK (recorded as “Other noncurrent liability” on the Company’s Balance Sheet for the year ended December 31, 2012)		$	2,314
	Issuance of common shares to GSK			30,268
	Cash received for common shares issued to GSK			(40,000	)
	Settlement of litigation with GSK			20,499
	Transaction costs			476
			$	13,557
	The components of the consideration transferred are described below:
		•		The cash payable to GSK represents the net present value of the annual payments to GSK of $1,000,000 for six years beginning in 2016.
		•		The Company recorded the issuance of common shares to GSK based on the Company’s closing stock prices on the respective stock issuance dates. The Company issued 1,841,112 and 2,190,100 common shares to GSK on November 8, 2012 and November 9, 2012, respectively.
		•		The termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the Company and GSK and effectively settled a preexisting relationship (see Note 1 for more information). As a result, the Company recorded a gain on the settlement of litigation, which represented foregone potential future monetary damages. This amount was valued based on a probability weighted scenario analysis that took into consideration the probability of each potential future alternative outcomes of the litigation between the parties.
		•		The transaction costs represent direct external costs incurred by the Company in connection with the November 2012 transaction.
	The consideration exchanged was recorded in the Company’s financial statements for the year ended December 31, 2012.
	On May 1, 2013, the Company obtained control of, and thus completed the acquisition of, the HORIZANT business. The acquisition constituted a business acquisition as defined under the provisions of the Business Combinations topic. Accordingly, the acquisition reflected the removal of the right to the HORIZANT business (which was recorded at fair value, as determined by a discounted cash flow analysis, that remained unchanged as of May 1, 2013), and the recording of the acquisition date fair values of the acquired inventory and manufacturing property and equipment assets. Assets acquired as a result of this transaction were as follows (in thousands):
	Inventories		$	11,733
	Manufacturing property and equipment			1,967
	Total assets acquired		$	13,700
	Inventories were comprised of acquired raw materials, specifically gabapentin enacarbil, and were valued using the cost approach. The cost approach provides a framework for estimating value based on the principle of substitution. The estimated fair value was calculated based on the costs to replace or reproduce the asset, including the cost of recrystallization of the raw material received, while considering any impact on the value of any obsolescence.
	Manufacturing property and equipment acquired included certain equipment and a dedicated manufacturing suite for use in the manufacture of HORIZANT and was recorded at fair value using the replacement cost method. The replacement cost method uses an estimate of the cost of replacing or reproducing an asset to measure value. This amount is then reduced to reflect the amount of depreciation that has accrued given the asset’s age. Other factors and adjustments were considered in concluding on the fair value, including obsolescence of the acquired assets. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, which is ten years.
	In 2013, the Company incurred $476,000 in transaction costs related to the HORIZANT business acquisition, which primarily consisted of legal, accounting and valuation-related expenses. These expenses were recorded in the “Selling, general and administrative” line of the “Operating expenses” section of the Company’s statements of comprehensive loss.
	As a result of the acquisition of the HORIZANT business, the Company recorded net revenues of $6,414,000 and a net loss of $21,522,000 associated with the HORIZANT business in the Company’s statements of comprehensive loss from the acquisition date through December 31, 2013.
	The following unaudited supplemental pro forma information summarizes the combined results of operations of the Company and the HORIZANT business as though the acquisition had occurred on January 1, 2012 (in thousands):
			Year Ended December 31,
			2013			2012
	Revenues		$	9,128		$	28,119
	Net loss		$	92,791		$	84,695
	These amounts have been calculated after applying the Company’s accounting policies and adjusting the results of the HORIZANT business to reflect the following adjustments:
		•		An amendment to depreciation expense included in costs of goods sold to reflect the depreciation of the fair value of the acquired manufacturing property and equipment over the estimated remaining useful lives of the respective assets.
		•		The difference between the cost of raw materials known as active pharmaceutical ingredient, or API, that GSK incurred and the Company’s recorded fair value of the API.
		•		The difference in selling expense between GSK direct selling expenses and the Company’s third party contractual costs.
	The pro forma information presented above is for informational purposes only and is not indicative of the results of operations that would have been achieved if the acquisition had taken place at the beginning of January 2012, nor is it indicative of any future results.

Cash_and_Cash_Equivalents_Shor

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments	12 Months Ended
	Dec. 31, 2013
Cash and Cash Equivalents, Short-Term Investments and Restricted Investments	'
	4	Cash and Cash Equivalents, Short-Term Investments and Restricted Investments
	The following are summaries of cash and cash equivalents, short-term investments and restricted investments (in thousands):
			Cost		Gross		Gross			Estimated
					Unrealized		Unrealized			Fair
					Gains		Losses			Value
	As of December 31, 2013:
	Cash		$	2,281	$	—	$	—		$	2,281
	Money market funds			10,046		—		—			10,046
	U.S. government-sponsored agencies			2,500		—		—			2,500
	Corporate debt securities			43,831		6		(6	)		43,831
	Certificates of deposit			1,725		—		—			1,725
			$	60,383	$	6	$	(6	)	$	60,383
	Reported as:
	Cash and cash equivalents									$	20,584
	Short-term investments										38,074
	Restricted investments										1,725
										$	60,383
			Cost		Gross		Gross			Estimated
					Unrealized		Unrealized			Fair
					Gains		Losses			Value
	As of December 31, 2012:
	Cash		$	915	$	—	$	—		$	915
	Money market funds			20,897		—		—			20,897
	U.S. government-sponsored agencies			11,329		1		—			11,330
	Corporate debt securities			105,839		32		(11	)		105,860
	Certificates of deposit			1,955		—		—			1,955
			$	140,935	$	33	$	(11	)	$	140,957
	Reported as:
	Cash and cash equivalents									$	36,134
	Short-term investments										102,868
	Restricted investments										1,955
										$	140,957
	At December 31, 2013 and 2012, the contractual maturities of all investments held were less than one year. All investments have been designated as available-for-sale, and changes to unrealized gains and losses are reflected as the only component of accumulated other comprehensive income. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company has classified all investments as short-term.
	No gross realized gains or losses were recognized in 2013, 2012 or 2011, and accordingly, there were no amounts reclassified out of accumulated other comprehensive income to earnings in 2013, 2012 or 2011.
	The Company’s available-for-sale investments, which include cash equivalents and short-term investments, are measured at fair value on a recurring basis and are classified at the following fair value hierarchy (see Note 1 for the Company’s accounting policy on measuring fair value of financial instruments) (in thousands):
					Fair Value Measurements at Reporting Date Using
	Description		Total As of		Quoted Prices in		Significant			Significant
			December 31,		Active Markets		Other			Unobservable
			2013		for Identical		Observable			Inputs
					Assets		Inputs			(Level 3)
					(Level 1)		(Level 2)
	Money market funds		$	10,046	$	10,046	$	—		$	—
	U.S. government-sponsored agencies			2,500		—		2,500			—
	Corporate debt securities			43,831		—		43,831			—
	Certificates of deposit			1,725		—		1,725
	Total		$	58,102	$	10,046	$	48,056		$	—
					Fair Value Measurements at Reporting Date Using
	Description		Total As of		Quoted Prices in		Significant			Significant
			December 31,		Active Markets		Other			Unobservable
			2012		for Identical		Observable			Inputs
					Assets		Inputs			(Level 3)
					(Level 1)		(Level 2)
	Money market funds		$	20,897	$	20,897	$	—		$	—
	U.S. government-sponsored agencies			11,330		—		11,330			—
	Corporate debt securities			105,860		—		105,860			—
	Certificates of deposit			1,955		—		1,955			—
	Total		$	140,042	$	20,897	$	119,145		$	—

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2013
Property and Equipment	'
	5	Property and Equipment
	Property and equipment consisted of the following (in thousands):
			December 31,
			2013			2012
	Laboratory equipment		$	10,701		$	11,478
	Manufacturing property and equipment			1,967			—
	Furniture and fixtures			1,107			1,283
	Computer equipment and software			5,475			5,679
	Leasehold improvements			3,344			4,596
	Construction in-progress			—			104
				22,594			23,140
	Less: Accumulated depreciation and amortization			(20,042	)		(21,612	)
	Property and equipment, net		$	2,552		$	1,528

Other_Accrued_Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2013
Other Accrued Liabilities	'
	6	Other Accrued Liabilities
	Other accrued liabilities at December 31, 2013 and December 31, 2012 were as follows (in thousands):
			December 31,		December 31,
			2013		2012
	Accrued product costs		$	1,903	$	—
	Accrued selling and marketing expenses			883		276
	Accrued general and administrative expenses			632		1,047
	Other liabilities			520		101
	Total other accrued liabilities		$	3,938	$	1,424

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2013
Restructuring	'
	7	Restructuring
	In December 2011, as part of the Company’s ongoing evaluation of its facilities requirements in light of future plans and in connection with the permanent cease use of the leased office space in a building at 3400 Central Expressway, Santa Clara, California, the Company recorded restructuring charges of $2,923,000 in accordance with the Exit or Disposal Cost Obligations topic of the Codification, which were included on a separate line in the Company’s statements of comprehensive loss for the year ended December 31, 2011. The restructuring charges consisted of $2,476,000 of facility-related charges and $447,000 of property and equipment write-offs. In the year ended December 31, 2012, the Company made cash payments of $1,737,000 and the remaining accrued restructuring charges were paid out in 2013. At December 31, 2012, the liability balance, included as “Accrued restructuring charges” on the balance sheets, was $993,000 and all was classified within current liabilities.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
	8	Commitments and Contingencies
	Operating Leases
	In February 2008, the Company entered into a lease for approximately 59,000 square feet of office space at 3400 Central Expressway, Santa Clara, California, the 3400 Lease. The term of the 3400 Lease extended to August 2013, which was 60 months from the date the premises were considered ready for occupation by the Company.
	Also in February 2008, the Company amended its lease with respect to the Company’s current office space at 3410 Central Expressway, Santa Clara, California, or, as amended, the 3410 Lease, that commenced in December 2001. This amendment extended the term of the 3410 Lease for approximately two years from the original expiration date of December 10, 2011, so that the 3410 Lease would expire in August 2013, on the same date as the 3400 Lease.
	In October 2012, the Company further amended the 3410 Lease to extend the term for an additional two years, so that the 3410 Lease will expire on August 27, 2015.
	In connection with the 3410 Lease, the Company entered into a letter of credit agreement of $1,500,000 in December 2006. The fair value of the certificate of deposit is presented as restricted investments on the balance sheet at $1,500,000 and $1,705,000 at December 31, 2013 and 2012, respectively. This letter of credit is required until the termination of the lease.
	The Company recognized rent expense on a straight-line basis over the applicable lease terms. Rent expense, excluding rent expense recognized as part of the restructuring charges recorded in 2011, was $2,626,000, $3,185,000 and $4,347,000 for the years ended December 31, 2013, 2012, and 2011 respectively. Deferred rent asset of $477,000 and $720,000 at December 31, 2013 and 2012, respectively, represented the difference between rent expense recognized and actual cash payments related to the Company’s operating leases. At December 31, 2013, deferred rent was comprised of a current deferred rent asset of $308,000 and a noncurrent deferred rent asset of $169,000. At December 31, 2012, deferred rent was comprised of a current deferred rent asset of $243,000 and a noncurrent deferred rent asset of $477,000.
	At December 31, 2013, future minimum payments under the Company’s non-cancelable operating lease were as follows (in thousands):
	Year ending December 31:
	2014		$	2,127
	2015			1,553
	Total minimum lease payments		$	3,680
	Guarantees and Indemnifications
	The Company, as permitted under Delaware law and in accordance with its bylaws, indemnifies its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity. The term of the indemnification period is for the officer’s or director’s lifetime. The Company may terminate the indemnification agreements with its officers and directors upon 90 days’ written notice, but termination will not affect claims for indemnification relating to events occurring prior to the effective date of termination. The maximum amount of potential future indemnification is unlimited; however, the Company has a director and officer insurance policy that limits its exposure and may enable it to recover a portion of any future amounts paid. The Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company had not recorded any liabilities for these agreements as of December 31, 2013.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity	'
	9.    Stockholders’ Equity
	Common Stock
	At December 31, 2013 and 2012, the Company was authorized to issue 100,000,000 shares of common stock.
	Stockholders’ Rights Plan
	On December 16, 2005, the Company adopted a preferred stock rights plan pursuant to which each share of the Company’s common stock outstanding has attached to it a preferred stock purchase right, or a right, that confers the right to purchase one one-hundredth of a share of Series A junior participating preferred stock at an exercise price of $140.00 per right, subject to adjustment, and will be exercisable only if a person or group acquires beneficial ownership of 15% or more of the Company’s common stock or announces a tender offer for 15% or more of the Company’s common stock. If such a person acquires 15% or more of the Company’s common stock, all rights holders, except such person, will be entitled to acquire the Company’s common stock at a discount through the exercise of the right. The rights plan has been designed to discourage acquisitions of more than 15% of the Company’s common stock without negotiations with the board of directors. The rights expire on January 13, 2016. The rights trade with the Company’s common stock, unless and until they are separated upon the occurrence of certain future events. The board of directors may terminate the rights plan at any time or redeem the rights prior to the time the rights are triggered.
	Equity Incentive Plans
	1999 Stock Plan
	Under the terms of the 1999 Stock Plan, or the 1999 Plan, options or stock purchase rights were granted by the board of directors to employees, directors and consultants. Options granted were either incentive stock options or non-statutory stock options. Incentive stock options were granted to employees with exercise prices of no less than the fair value, and non-statutory options were granted to employees, directors or consultants at exercise prices of no less than 85% of the fair value, of the common stock on the grant date as determined by the board of directors. Options vest as determined by the board of directors, generally at the rate of 25% at the end of the first year, with the remaining balance vesting ratably over the next three years for initial employee grants and ratably over four years for subsequent grants. Options granted under the 1999 Plan expire no more than ten years after the date of grant. All options granted under the 1999 Plan have vested.
	2005 Equity Incentive Plan
	In January 2005, the Company’s board of directors adopted the 2005 Equity Incentive Plan, or the 2005 Plan. Under the terms of the 2005 Plan, options, stock purchase rights, stock bonus rights, stock appreciation rights and other stock awards and rights may be granted by the board of directors to employees, directors and consultants. Options granted may be either incentive stock options or non-statutory stock options. Incentive stock options may be granted to employees with exercise prices of no less than the fair value, and non-statutory options may be granted to employees, directors or consultants at exercise prices of no less than 85% of the fair value, of the common stock on the grant date. Options vest as determined by the board of directors, generally at the rate of 25% at the end of the first year, with the remaining balance vesting ratably over the next three years for initial employee grants and ratably over four years for subsequent grants. Options granted under the 2005 Plan expire no more than ten years after the date of grant.
	In January 2007, the Company’s board of directors approved the use of grants of restricted stock units to employees, directors or consultants under the 2005 Plan as part of the Company’s long-term incentive compensation program. Restricted stock units have no exercise price, are valued using the closing market price on the date of grant and vest as determined by the board of directors, typically either: (i) in annual tranches over a four-year period at the rate of 25% at the end of each year; (ii) in annual tranches over a three-year period at the rate of 25%, 25% and 50%, respectively, at the end of each year; or (iii) in one tranche on the one-year anniversary of the grant date. Employees can elect to have the Company withhold a portion of shares to pay for their payroll taxes in connection with the vesting of restricted stock units, where the Company would then make a cash payment for the associated payroll taxes on behalf of the employees, or employees can elect to make the cash payment for the associated payroll taxes.
	In May 2010, the Company granted performance stock unit awards to two executive employees. Each performance stock unit award was scheduled to vest three years from the grant date, with the actual number of shares of common stock of the Company subject to issuance to be between 0% and 200% of the target amount, based on the performance of the Company’s total shareholder return as compared to the total shareholder returns of a group of pre-selected pharmaceutical companies over a performance period ending on the third anniversary of the grant date. The target amount of shares of common stock of the Company that were subject to issuance under the performance stock unit awards was 140,000, and the grant date fair value using a lattice valuation model of these performance stock unit awards was $2,675,000. In 2010, a performance stock unit award representing a target amount of 40,000 shares was cancelled due to the departure of one of the two executive employees. In 2013, 97,300 shares were cancelled based on the performance of the Company’s total shareholder return as compared to the total shareholder returns of a group of pre-selected pharmaceutical companies over the three year performance period. At December 31, 2013, there were no shares outstanding, and the associated expense recognized in the year ended December 31, 2013, 2012 and 2011 was $232,000, $638,000 and $636,000, respectively.
	Stock purchase rights, stock bonus rights, stock appreciation rights and other stock awards and rights may be granted by the board of directors to employees, directors and consultants and may be subject to such terms and conditions as the board of directors deems appropriate, although such awards may not be granted with a purchase price below the par value of the stock. Under the terms of the 2005 Plan, the maximum number of shares that may be issued shall not exceed the total of 2,000,000, plus any shares issuable from options previously granted from the 1999 Plan at the date of the Company’s initial public offering, plus an annual increase equal to the lesser of (i) 2.5% of the total number of common shares outstanding at the end of the preceding calendar year and (ii) 2,000,000 common shares. During the year ended December 31, 2013, the annual increase to the 2005 Plan reserve was 1,176,691 shares. At December 31, 2013 and 2012, there were 1,810,768 and 1,208,954 shares, respectively, remaining and available for future grant under the 2005 Plan.
	New Employee Inducement Stock Awards
	In May 2008, the Company’s Senior Vice President and Chief Commercialization Officer was granted a new employee inducement stock award outside of the Company’s stockholder-approved equity plans consisting of nonqualified stock options to purchase 140,612 shares of the Company’s common stock. The stock options have a per share exercise price of $42.59, the closing trading price of the Company’s common stock on the NASDAQ Global Market on the May 1, 2008 grant date. The stock options have a ten-year term and vested over four years, with 25% cliff vesting on the first anniversary of the May 1, 2008 grant date, and 1/48th of the shares subject to the options vesting monthly thereafter. The Company also granted to the Company’s Senior Vice President and Chief Commercialization Officer a new employee inducement stock award outside of the Company’s stockholder-approved equity plans consisting of restricted stock units for 10,000 shares of the Company’s common stock. The restricted stock units vested in four equal annual installments on each anniversary of the May 1, 2008 grant date.
	2010 Inducement Award Plan
	In May 2010, the Company’s board of directors adopted the 2010 Inducement Award Plan, or the 2010 Inducement Plan. Under the terms of the 2010 Inducement Plan, options, stock purchase awards, stock bonus awards, stock appreciation rights, stock unit awards and other stock awards may be granted by the board of directors or the independent compensation committee of the board of directors to persons entering into employment with the Company and not previously employees or directors of the Company (or following bona fide periods of non-employment with the Company) as an inducement material to the new employees entering into employment with the Company in accordance with NASDAQ Market Place Rule 5635(c)(4). Options granted may be non-statutory stock options with exercise prices of no less than 100% of the fair value of the Company’s common stock on the grant date. Options vest as determined by the board of directors or the compensation committee of the board of directors, generally at the rate of 25% at the end of the first year, with the remaining balance vesting ratably over the next three years. Options granted under the 2010 Inducement Plan expire no more than ten years after the date of grant. Restricted stock units have no exercise price, are valued using the closing market price on the date of grant and vest as determined by the board of directors or the compensation committee of the board of directors, typically in annual tranches over a four-year period at the rate of 25% at the end of each year.
	A total of 350,000 shares of common stock were initially authorized for issuance under the 2010 Inducement Plan, and an additional 625,000 shares were authorized for issuance in 2011. Under the terms of the 2010 Inducement Plan, the maximum number of shares that may be issued shall not exceed the total of 975,000. At December 31, 2013 and 2012, there were 365,686 and 752,901 shares, respectively, remaining and available for future grant under the 2010 Inducement Plan.
	2005 Non-Employee Directors’ Stock Option Plan
	In January 2005, the Company’s board of directors adopted the 2005 Non-Employee Directors’ Stock Option Plan, or the 2005 Directors’ Plan, under which non-statutory options are automatically granted to non-employee directors. Before May 1, 2012, any individual who first became a non-employee director automatically received an option to purchase 25,000 shares subject to vesting in four equal successive annual installments. Effective May 1, 2012, any individual who first becomes a non-employee director automatically receives an option to purchase 30,000 shares subject to vesting in 24 successive equal monthly installments. Prior to May 1, 2012, non-employee directors serving on the date of each annual meeting of stockholders received an option to purchase 10,000 shares subject to vesting in 12 successive equal monthly installments measured from the grant date. Effective May 1, 2012, non-employee directors serving on the date of each annual meeting of stockholders receive an option to purchase 15,000 shares subject to vesting in 12 successive equal monthly installments measured from the grant date. Stock options may be granted at exercise prices no less than the fair value on the grant date and may expire no more than ten years after the date of grant. Under the terms of the 2005 Directors’ Plan, the maximum number of shares that may be issued shall not exceed the total of 150,000, plus an annual increase equal to the excess of (i) the number of shares subject to options granted in the preceding calendar year, over (ii) the number of shares added back to the share reserve from cancellations, provided that such increase shall not exceed 150,000 shares. During the year ended December 31, 2013, the annual increase to the 2005 Directors’ Plan reserve was 135,000 shares. At December 31, 2013 and 2012, there were 30,000 and 15,000 shares, respectively, remaining and available for future grant under the 2005 Directors’ Plan.
	A summary of option activity as of and for the year ended December 31, 2013 is presented below:
		Shares			Weighted-		Weighted-		Aggregate
					Average		Average		Intrinsic
					Exercise		Remaining		Value
					Price		Contractual
							Term
									(In thousands)
	Outstanding at January 1, 2013		4,460,348		$	19.19
	Options granted		1,198,500		$	7.91
	Options cancelled		(199,706	)	$	22.61
	Options exercised		(90,178	)	$	3.45
	Outstanding at December 31, 2013		5,368,964		$	16.81		5.81	$	(989,933	)
	Exercisable at December 31, 2013		3,968,914		$	20.1		4.81	$	(644,975	)
	A summary of restricted stock and performance stock unit activity for the year ended December 31, 2013 is presented below:
		Shares			Weighted-
					Average
					Grant Date
					Fair Value
	Outstanding at January 1, 2013		1,878,424		$	7.25
	Awards granted		681,500		$	8.13
	Awards cancelled		(302,662	)	$	10.95
	Awards vested		(802,072	)	$	7.73
	Outstanding at December 31, 2013		1,455,190		$	7.15
	The Company expected that the number of options and restricted stock units that will ultimately vest will be materially similar to the number of options and restricted stock units outstanding at December 31, 2013.
	The aggregate intrinsic value of all options outstanding and exercisable at December 31, 2013 was based on a closing stock price of $5.75.
	The weighted-average grant date fair values of options granted in the years ended December 31, 2013, 2012 and 2011 were $5.22, $3.12 and $5.26 per share, respectively. The weighted-average grant date fair values of restricted stock units granted in the years ended December 31, 2013, 2012 and 2011 were $8.13, $5.22, and $9.04 per share, respectively.
	The total intrinsic value of options exercised in the years ended December 31, 2013, 2012 and 2011 was $304,000, $137,000 and $20,000, respectively. The total fair value of restricted stock units that vested in the year ended December 31, 2013, 2012 and 2011 was $6,202,053, $4,372,000 and $3,406,000, respectively.
	As of December 31, 2013, the total compensation cost related to 1,400,050 unvested options and unvested awards’ covering 1,455,190 shares not yet recognized was $12,279,000. This amount will be recognized over an estimated weighted-average amortization period of 2.37 years.
	Employee Stock Purchase Plan
	As of December 31, 2013, the Company had reserved a total of 1,195,555 shares of common stock for issuance under the ESPP. In addition, the board of directors may increase the share reserve as of each January 1 through January 1, 2015, by an amount not to exceed the lesser of (i) 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year or (ii) 250,000 shares. The ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. The price at which the stock is purchased is equal to the lower of 85% of the fair market value of the common stock at the beginning of an offering period or after a purchase period ends. During the years ended December 31, 2013 and 2012, 142,455 shares and 185,249 shares, respectively, were purchased under the ESPP. During the year ended December 31, 2013, the annual increase to the ESPP was 250,000 shares. At December 31, 2013 and 2012, there were 255,602 and 148,057 shares, respectively, remaining and available for future grant under the ESPP.
	Warrants
	At December 31, 2013, 283,420 warrants were outstanding and exercisable for shares of common stock at $25.40 per share. The warrants expired unexercised at midnight on December 31, 2013.

Preferred_Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2013
Preferred Stock	'
	10	Preferred Stock
	At December 31, 2013 and 2012, the Company was authorized to issue 5,000,000 shares of preferred stock, of which 1,000,000 shares were authorized for issuance as Series A junior participating preferred stock.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
	11	Income Taxes
	Deferred income taxes reflect the net tax effects of NOL and tax credit carryovers and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s net deferred tax assets were as follows (in thousands):
			December 31,
			2013			2012
	Net operating loss carryforwards		$	161,663		$	130,104
	Research credit carryforwards			30,111			29,847
	Capitalized research and development			5,579			7,638
	Deferred revenue			4,700			4,994
	Stock options			14,672			15,881
	Other			1,605			2,656
	Total net deferred tax assets			218,330			191,120
	Valuation allowance			(218,330	)		(191,120	)
	Net deferred tax assets		$	—		$	—
	Realization of net deferred tax assets is dependent upon the Company generating future taxable income, the timing and amount of which are uncertain. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $27,210,000, $6,259,000 and $12,301,000 during 2013, 2012 and 2011, respectively.
	As of December 31, 2013, the Company had NOL carryforwards for federal income tax purposes of $414,870,000, which expire in the years 2022 through 2033, and federal research and development tax credits of $23,177,000, which expire in the years 2021 through 2033.
	As of December 31, 2013, the Company had NOL carryforwards for state income tax purposes of $308,758,000, which expire in the years 2014 through 2033, and state research and development tax credits of $12,009,000, which do not expire.
	Approximately $529,000 of the valuation allowance for net deferred tax assets relates to benefits of stock option deductions that, when recognized, will be allocated directly to additional paid-in capital.
	The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. To date, the Company has not been audited by the Internal Revenue Service or any state income tax jurisdiction. Tax years 2003 to 2013 remain subject to examination by the U.S. federal jurisdiction and various state jurisdictions.
	Utilization of the Company’s NOL and credit carryforwards may be subject to substantial annual limitation due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. Such annual limitation could result in the expiration of the net operating loss and credit carryforwards before utilization. As of December 31, 2013, based on the analyses performed on annual limitation as a result of ownership changes that may have occurred from inception through December 2012, the Company expects to be able to use all of the NOL and tax credit carryforwards before their respective expiration periods.
	The Company’s unrecognized tax benefits relate to state research and development tax credits claimed on the Company’s state tax returns. The state research and development tax credits have not been utilized, are fully offset by a valuation allowance and currently have no tax impact.
	A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
	January 1, 2013		$	—
	Increases related to current year tax positions			1,340,000
	December 31, 2013		$	1,340,000

RelatedParty_Transaction

Related-Party Transaction	12 Months Ended
	Dec. 31, 2013
Related-Party Transaction	'
	12	Related-Party Transaction
	In May 2011, the Company engaged McKinsey & Company, Inc. to provide consulting services to the Company. Jon R. Duane, a director of McKinsey, is the spouse of Catherine J. Friedman, a member of the Company’s Board of Directors. The Company expensed $1,011,000 through December 31, 2011 in connection with this engagement and none in 2012 and 2013.

Quarterly_Financial_Data_Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Data (Unaudited)	'
	13.    Quarterly Financial Data (Unaudited)
	The following table summarizes the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share data):
			Quarter Ended
			Dec. 31,			Sept. 30,			June 30,			March 31,			Dec. 31,		Sept. 30,			June 30,			March 31,
			2013			2013			2013			2013			2012(1)		2012			2012			2012
	Selected Quarterly Data:
	Total revenues		$	2,879		$	2,527		$	2,086		$	459		$	487	$	379		$	10,379		$	10,379
	Net income (loss)		$	(19,138	)	$	(18,816	)	$	(24,381	)	$	(23,548	)	$	3,042	$	(16,753	)	$	(7,959	)	$	(9,144	)
	Basic and diluted net income (loss) per share		$	(0.40	)	$	(0.39	)	$	(0.51	)	$	(0.50	)	$	0.07	$	(0.41	)	$	(0.22	)	$	(0.26	)
	-1	The termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the Company and GSK and effectively settled a preexisting relationship (see Note 1 for more information). As a result, the Company recorded a gain on the settlement of litigation (see Note 3 for more information).

Subsequent_Event

Subsequent Event	12 Months Ended
	Dec. 31, 2013
Subsequent Event	'
	14	Subsequent Event
	On January 29, 2014, the Company completed an underwritten public offering of 12,000,000 shares of its common stock at a price to the public of $6.00 per share. Net cash proceeds from the public offering were approximately $67,300,000, after deducting the underwriting discounts and commissions and offering expenses payable by the Company. On February 21, 2014, the underwriters exercised in full their over-allotment option of 1,800,000 shares resulting in cash proceeds of approximately $10,100,000, after deducting the underwriting discounts and commissions and offering expenses payable by the Company.

Organization_and_Summary_of_Si1

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Basis of Preparation	'
	Basis of Preparation
	The Company’s financial statements are prepared in accordance with the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or the Codification, which is the single source of authoritative U.S. generally accepted accounting principles, or GAAP.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates.
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	The carrying amounts of certain of the Company’s financial instruments, including cash and cash equivalents and short-term investments, restricted investments, accounts receivables and accounts payable, approximate their fair value due to their short-term maturities. The Company accounts for the fair value of its financial instruments in accordance with the provisions of the Fair Value Measurement topic of the Codification.
	Fair value is the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The Company applies the market approach valuation technique for fair value measurements on a recurring basis and attempts to maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. All of the Company’s cash equivalents and short-term investments are measured using inputs classified at Level 1 or Level 2 within the fair value hierarchy. Level 1 inputs are quoted prices in active markets for identical assets. Level 2 inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Level 3 inputs are unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes and market reference data.
Cash Equivalents and Short-Term Investments	'
	Cash Equivalents and Short-Term Investments
	The Company considers all highly liquid investments with original maturities of 90 days or less at the time of purchase to be cash equivalents, which primarily consist of money market funds, U.S. government-sponsored agencies and corporate debt securities.
	Management determines the appropriate classification of securities at the time of purchase. All investments have been designated as available-for-sale. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company has classified all investments as short-term, even though the stated maturity may be one year or more beyond the current balance sheet date. Available-for-sale securities are carried at estimated fair value with unrealized gains and losses reported as a component of other comprehensive loss in the statements of comprehensive loss.
	The cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities, if any, are recorded in interest income and expense. The cost of securities sold is based on the specific-identification method. Interest and dividends are included in interest income.
Restricted Investments	'
	Restricted Investments
	Under a facilities operating lease agreement, the Company is required to secure a letter of credit with cash or securities. At December 31, 2013 and 2012, the Company recorded $1,500,000 and $1,705,000, respectively, of restricted investments related to the letter of credit (see Note 8 for more information).
	In connection with the Company’s license to use radioactive materials in its research facilities, it must maintain a $225,000 letter of credit with the Radiological Health Branch of the State of California. This requirement has been fulfilled through certificates of deposit with a financial institution. The fair value of the secured amount of $225,000 and $250,000 was classified as restricted investments in the accompanying balance sheets at both December 31, 2013 and 2012.
Segment Information	'
	Segment Information
	The Company operates in one operating segment, which is the development and commercialization of product candidates for the potential treatment of neurological and other disorders, and has operations solely in the United States. To date, all of the Company’s revenues from product sales are related to sales of HORIZANT in the United States. The Company has recognized up-front license payment and royalty revenue under its collaboration agreement with Astellas Pharma Inc. (see Note 2 for more information on the collaboration agreement).
Concentrations of Risk	'
	Concentrations of Risk
	The Company invests cash that is not being used for operational purposes. This exposes the Company to credit risk in the event of default by the institutions holding the cash and cash equivalents and available-for-sale securities. The credit risk is mitigated by the Company’s investment policy, which allows for the purchase of low risk debt securities issued by the U.S. government, U.S. government-sponsored agencies and highly rated banks and corporations, subject to certain concentration limits. The maturities of these securities are maintained at no longer than 18 months. The Company believes its established guidelines for investment of its excess cash enhances safety and liquidity through its policies on diversification and investment maturity.
	Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and available-for-sale investment securities in high-credit quality debt securities issued by the U.S. government, U.S. government-sponsored enterprises and highly rated banks and corporations. The carrying amounts of cash equivalents and available-for-sale investment securities are stated at fair value.
	The Company is subject to credit risk from its accounts receivable related to product sales. The Company’s trade accounts receivable arises from product sales in the United States. Three wholesale distributors represented 47%, 33% and 16% of product sales for the year ended December 31, 2013. These three customers individually comprised 45%, 29% and 22%, respectively, of product sales related to accounts receivable as of December 31, 2013. Accounts receivable balances related to product sales were $939,000 for the year ended December 31, 2013. The Company did not have product sales and accounts receivable as of December 31, 2012. To date, the Company has not experienced any losses with respect to the collection of its accounts receivable and believes that its accounts receivable are collectible.
	The Company relies on a single third-party contract manufacturer organization to manufacture HORIZANT.
Property and Equipment	'
	Property and Equipment
	Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, which is generally five to ten years for the Company’s laboratory equipment, furniture and fixtures and manufacturing property and equipment and generally three years for the Company’s computer equipment and software. Leasehold improvements are amortized over their estimated useful lives or the remaining lease term, whichever is shorter.
Revenue Recognition	'
	Revenue Recognition
	Product Sales
	The Company began selling HORIZANT to wholesalers in May 2013 following the return of the Company’s commercial rights from GSK. The Company recognizes revenue from HORIZANT product sales when there is persuasive evidence that an arrangement exists, delivery to the customer has occurred, the price is fixed or determinable and collectability is reasonably assured. Revenue from product sales is recorded net of estimated allowances for customer incentives such as cash discounts for prompt payment, distributor fees, expected returns, as appropriate (which are based on an analysis of historical return rates and deductions of HORIZANT, since its commercial launch by GSK in the second quarter of 2011), government rebates such as Medicaid reimbursements and patient assistance programs. Calculating certain of these items involves estimates and judgments based on contractual terms, historical utilization rates data for HORIZANT and new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future utilization rates for these programs and channel inventory data. If future actual results vary from the Company’s estimates, the Company may need to adjust these estimates, which could have an effect on product sales and earnings in the period of adjustment.
	Items Deducted from Gross Product Sales
	Prompt Pay Discount
	The Company offers cash discounts to its customers, generally 2% of the sales price, as an incentive for prompt payment. Based on GSK’s commercialization experience, the Company expects customers to continue to comply with the prompt payment terms to earn the cash discount as the Company is selling HORIZANT to the same customers under similar prompt payment terms and conditions. The Company estimates cash discounts for prompt payment based on contractual terms, GSK’s historical customer utilization rates and the Company’s historical customer utilization rates. The Company accounts for cash discounts by reducing accounts receivable by the full amount and recognizing the discount as a reduction of revenue in the same period the related revenue is recognized.
	Distributor Fees
	Under the Company’s inventory management agreements with significant wholesalers, the Company pays the wholesalers a fee primarily for distribution services as well as the maintenance of inventory levels. These distributor fees are based on a contractually determined fixed percentage of sales. The Company accrues the contractual amount and recognizes the discount as a reduction of revenue in the same period the related revenue is recognized.
	Product Returns
	The Company does not provide its customers with a general right of product return, but permits returns if the product is damaged or defective when received by the customer, or if the product has or is nearly expired. HORIZANT tablets currently have a shelf-life of 36 months from the date of manufacture. The Company will accept returns for products that will expire within six months or that have expired up to one year after their expiration dates. The Company obtained actual return history by type from GSK since GSK’s product launch in 2011, which provides a basis to reasonably estimate the Company’s future product returns. The Company estimates returns taking into consideration Company-specific adjustments to GSK’s returns history, the shelf life of product, shipment and prescription trends and estimated distribution channel inventory levels.
	Government Rebates and Chargebacks
	The Company participates in a number of government rebate programs, such as the Medicaid Drug Rebate Program that provides assistance to eligible low-income patients based on each individual state’s guidelines regarding eligibility and services, Public Health Services or 340b programs, and the Medicare Part D Coverage Gap Discount Program, which provides rebates on prescriptions that fall within the “donut hole” coverage gap; and the Department of Veterans Affairs that offers discounts to authorized users of HORIZANT. HORIZANT is also listed on the Federal Supply Schedule, or FSS, of the General Services Administration which provides a discount to the Department of Defense, Department of Veterans Affairs, and TriCare. The Company estimates reductions to the Company’s revenues for government rebate programs based on product pricing, current rebates, GSK’s historical utilization rates, the Company’s actual utilization rates, new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future rebates for these programs and estimated levels of inventory in the distribution channel.
	Patient Assistance
	The Company offers a co-pay card program to assist commercially insured patients with the cost of their HORIZANT related co-payments. Participating retail pharmacies get reimbursed by the Company for the amount of the co-pay assistance provided to eligible patients. The Company estimates and accrues the cost of the co-pay program based on historical redemption activity for this program. The Company reimburses the participating pharmacies approximately one month after the prescriptions subject to co-pay assistance are filled.
	Multiple-Element Arrangements
	Revenue arrangements are accounted for in accordance with the provisions of the Revenue Recognition-Multiple-Element Arrangements topic of the Codification.
	In evaluating arrangements with multiple elements, the Company considers whether components of the arrangement represent separate units of accounting based upon whether certain criteria are met, including whether the delivered element has stand-alone value to the customer and whether there is objective and reliable evidence of the fair value of the undelivered items. This evaluation requires subjective determinations and requires management to make judgments about the fair value of individual elements and whether such elements are separable from other aspects of the contractual relationship. The consideration received in such arrangements is allocated among the separate units of accounting based on the relative selling price method under which the selling price for each deliverable is determined using vendor-specific objective evidence of selling price, if it exists; otherwise, third-party evidence of selling price. If vendor-specific objective evidence and third-party evidence of selling price are not available for a deliverable, the Company will use its best estimate of the selling price for that deliverable when applying the relative selling price method. The applicable revenue recognition criteria are applied to each of the separate units.
	Revenues from multiple deliverables combined as a single unit of accounting are deferred and recognized over the period during which the Company remains obligated to perform services. The specific methodology for the recognition of the revenue (e.g., straight-line or according to specific performance criteria) is determined on a case-by-case basis according to the facts and circumstances applicable to a given agreement.
	Payments received in excess of revenues recognized are recorded as deferred revenue until such time as the revenue recognition criteria have been met.
	Collaboration revenue includes revenue from the Company’s current collaboration agreement with Astellas Pharma Inc. Net revenue from unconsolidated joint operating activities included all revenue that resulted solely from the Company’s terminated collaboration agreement with GSK. The Company accounts for the revenue-related activities of these collaboration agreements as follows:
		•		Up-front, licensing-type payments. Up-front, licensing-type payments are assessed to determine whether or not the licensee is able to obtain any stand-alone value from the license. Where this is not the case, the Company does not consider the license deliverable to be a separate unit of accounting, and the revenue is deferred with revenue recognition for the license fee being assessed in conjunction with the other deliverables that constitute the combined unit of accounting.
		•		Milestones. Revenue recognition will occur only if the consideration earned from the achievement of a milestone meets all the criteria for the milestone to be considered substantive at the inception of the arrangement, such that it: (i) is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company’s performance to achieve the milestone; (ii) relates solely to past performance; and (iii) is reasonable relative to all deliverables and payment terms in the arrangement.
	The Company will assess the nature of contingent payments, and appropriate accounting for, these payments on a case-by-case basis in accordance with the provisions of the Revenue Recognition topic of the Codification.
		•		Profit and loss sharing. This represented the Company’s share of the profits and losses from the co-promotion of HORIZANT with GSK under the terminated collaboration with GSK. Amounts were recognized in the period in which the related activities occurred, and their financial statement classification was based on the Company’s assessment that these activities constituted part of the Company’s ongoing central operations.
		•		Product royalties. The Company is entitled to receive royalties on net sales of gabapentin enacarbil (known as REGNITE) in Japan. Astellas initiated sales of REGNITE in Japan in July 2012, and the Company recognizes the associated product royalties when they can be reliably measured and collectability is reasonably assured (generally upon receipt of the royalty payment).
Cost of Product Sales	'
	Cost of Product Sales
	Cost of product sales includes direct and indirect costs to manufacture product sold, including tableting, packaging, storage, shipping and handling costs and inventory write-downs, if any.
Accounts Receivable	'
	Accounts Receivable
	Trade accounts receivable are recorded net of allowances for cash discounts for prompt payment, wholesaler discounts and chargebacks. The need for bad debt allowance is evaluated each reporting period based on the Company’s assessment of the credit worthiness of its customers.
Inventories	'
	Inventories
	Inventories are stated at the lower of cost or market. Cost is determined on a first-in, first-out, or FIFO, basis. The Company regularly evaluates the Company’s inventories for excess quantities and obsolescence (expiration), taking into account such factors as historical and anticipated future sales compared to quantities on hand and the remaining shelf life of HORIZANT. Write-downs of inventories are considered to be permanent reductions in the cost basis of inventories.
	Inventories that are not expected to be consumed within 12 months following the balance sheet date are classified as long-term inventories.
	Inventories as of December 31, 2013 were summarized as follows (in thousands):
	Raw materials		$	10,258
	Work in progress			76
	Finished goods			1,113
	Total inventory			11,447
	Less: Long-term inventories			10,185
	Total inventory classified as current		$	1,262
	Long-term inventories consist of Active Pharmaceutical Ingredient, or API, of gabapentin enacarbil used for production of the Company’s product HORIZANT. The Company evaluates demand for HORIZANT and expected consumption of the API based on long-term projected sales of HORIZANT.
	The Company did not have inventories as of December 31, 2012.
Research and Development	'
	Research and Development
	All research and development costs, including those funded by third parties, are expensed as incurred. Research and development costs consist of salaries, employee benefits, laboratory supplies, costs associated with clinical trials, including amounts paid to clinical research organizations, other professional services and facility costs.
Clinical Trials	'
	Clinical Trials
	The Company accrues and expenses the costs for clinical trial activities performed by third parties based upon estimates of the percentage of work completed over the life of the individual study in accordance with agreements established with contract research organizations and clinical trial sites. The Company determines the estimates through discussions with internal clinical personnel and external service providers as to progress or stage of completion of trials or services and the agreed upon fee to be paid for such services. Costs of setting up clinical trial sites for participation in the trials are expensed immediately as research and development expenses. Clinical trial site costs related to patient visits are accrued as patients progress through the trial and are reduced by any payments made to the clinical trial site. Non-refundable advance payments for research and development goods or services are recognized as expense as the related goods are delivered or the related services are provided in accordance with the provisions of the Research and Development Arrangements topic of the Codification.
Nonretirement Postemployment Benefits	'
	Nonretirement Postemployment Benefits
	On May 31, 2012, the Company adopted the XenoPort Amended and Restated 2012 Severance Plan, or the 2012 Severance Plan, for the benefit of the Company’s non-executive employees. Under the terms of the 2012 Severance Plan, a non-executive employee terminated by the Company because of elimination of his or her position is eligible to receive continuation of medical insurance under COBRA and specified severance payments based on the employee’s level and years of service with the Company. The Company accounts for employee termination benefits in accordance with the provisions of the Compensation-Nonretirement Postemployment Benefits topic of the Codification and records employee termination liabilities once they are both probable and estimable for severance provided under the Company’s existing severance program.
	On June 14, 2013, the Company implemented a reduction in force that included the elimination of certain non-executive positions as the Company completed certain work projects on its arbaclofen placarbil development program. As a result, the Company recorded severance benefits charges of $703,000 in 2013, which were included in the “Research and development” line of the “Operating expenses” section of the Company’s statements of comprehensive loss. As of December 31, 2013, there was no associated liability balance.
Stock-Based Compensation	'
	Stock-Based Compensation
	The Compensation — Stock Compensation topic of the Codification establishes accounting for stock-based awards exchanged for employee services. In accordance with this topic, for stock options, awards and stock purchase rights under the Company’s employee stock purchase plan, or ESPP, stock-based compensation cost is measured at grant date, based on the fair value of the award, and is recognized as expense over the requisite employee service period.
	The effect of recording stock-based compensation under the Compensation — Stock Compensation topic was as follows:
			Year Ended December 31,
			2013			2012			2011
			(In thousands, except
			per share amounts)
	Stock-based compensation by type of award:
	Employee stock options and awards		$	10,083		$	11,956		$	14,044
	ESPP			461			325			344
	Total stock-based compensation		$	10,544		$	12,281		$	14,388
	Effect on basic and diluted net loss per share		$	(0.22	)	$	(0.31	)	$	(0.41	)
	The Company’s employee non-cash stock-based compensation was reported as follows:
			Year Ended December 31,
			2013			2012			2011
			(In thousands)
	Research and development		$	3,059		$	4,364		$	5,208
	Selling, general and administrative			7,485			7,917			9,180
			$	10,544		$	12,281		$	14,388
	Valuation Assumptions
	The Company estimates the fair value of all of its stock options and stock purchase rights on the date of grant using a Black-Scholes valuation model that requires the input of highly subjective assumptions, including the option’s expected life and the price volatility of the underlying stock. The Company derived the expected life assumptions using data obtained from similar entities, taking into consideration factors such as industry, stage of life cycle, size and financial leverage. The Company has determined that its historical volatility can be used to derive the expected stock price volatility assumption. The Company expenses the resulting charge using the straight-line attribution method over the vesting period. Restricted stock units are measured at the fair value of the Company’s common stock on the date of grant and expensed over the period of vesting using the straight-line attribution approach. The calculation of the Black-Scholes valuations used the following weighted-average assumptions:
			Year Ended December 31,
			2013		2012	2011
	Dividend yield		0%		0%	0%
	Volatility for options		0.82		0.81	0.77
	Volatility for ESPP		0.59		0.65	0.73
	Weighted-average expected life of options (years)		5.25		5.09	5.34
	Weighted-average expected life of ESPP rights (years)		0.5		0.5	0.5
	Risk-free interest rate for options		0.70-1.60%		0.62-1.02%	0.90-2.26%
	Risk-free interest rate for ESPP rights		0.07-0.17%		0.07-0.27%	0.07-0.19%
	The Black-Scholes option-pricing model was developed for use in estimating the fair value of short-lived, exchange-traded options that have no vesting restrictions and are fully transferable.
Income Taxes	'
	Income Taxes
	Income taxes are accounted for in accordance with the Income Taxes topic of the Codification using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is more-likely-than-not that the deferred tax assets will not be realized.
	The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at the reporting date.
	As of December 31, 2013, the Company had unrecognized tax benefits and expects no significant changes in unrecognized tax benefits in the next 12 months (see Note 11 for more information).
	The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense. To date, there have been no interest or penalties charged to the Company in relation to the underpayment of income taxes.
Comprehensive Loss	'
	Comprehensive Loss
	The Company presents all non-owner changes in stockholders’ equity in a single continuous statement of comprehensive loss and shows: (i) each component of net loss along with total net loss; (ii) each component of other comprehensive loss along with a total for other comprehensive loss; and (iii) a total amount for comprehensive loss. The Company’s other comprehensive loss is comprised of unrealized gains (losses) on available-for-sale securities.
Advertising Costs	'
	Advertising Costs
	Advertising costs, included in selling, general and administrative expenses, are charged to expense as incurred. Advertising expenses for the year ended December 31, 2013, was $8,244,000. The Company did not have advertising costs for the years ended December 31, 2012 and 2011.
Net Loss Per Share	'
	Net Loss Per Share
	Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period without consideration for potential common shares. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period plus any dilutive potential common shares for the period determined using the treasury-stock method. For purposes of this calculation, restricted stock units, options to purchase stock and warrants are considered to be potential common shares and are only included in the calculation of diluted net loss per share when their effect is dilutive.
			Year Ended December 31,
			2013			2012			2011
			(In thousands, except
			per share amounts)
	Numerator:
	Net loss		$	(85,883	)	$	(30,814	)	$	(33,380	)
	Denominator:
	Weighted-average common shares outstanding			47,545			39,434			35,400
	Basic and diluted net loss per share		$	(1.81	)	$	(0.78	)	$	(0.94	)
	Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
	Restricted stock units and options to purchase common stock			6,824			6,339			5,903
	Warrants outstanding			283			283			305
				7,107			6,622			6,208

Organization_and_Summary_of_Si2

Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Inventory	'
	Inventories as of December 31, 2013 were summarized as follows (in thousands):
	Raw materials	$	10,258
	Work in progress		76
	Finished goods		1,113
	Total inventory		11,447
	Less: Long-term inventories		10,185
	Total inventory classified as current	$	1,262
Stock-Based Compensation by Type of Award	'
	The effect of recording stock-based compensation under the Compensation — Stock Compensation topic was as follows:
		Year Ended December 31,
		2013			2012			2011
		(In thousands, except
		per share amounts)
	Stock-based compensation by type of award:
	Employee stock options and awards	$	10,083		$	11,956		$	14,044
	ESPP		461			325			344
	Total stock-based compensation	$	10,544		$	12,281		$	14,388
	Effect on basic and diluted net loss per share	$	(0.22	)	$	(0.31	)	$	(0.41	)
Employee Non-Cash Stock-Based Compensation Excluding Non-Cash Stock-Based Compensation Resulting from Twenty Ten Restructuring Plan	'
	The Company’s employee non-cash stock-based compensation was reported as follows:
		Year Ended December 31,
		2013			2012			2011
		(In thousands)
	Research and development	$	3,059		$	4,364		$	5,208
	Selling, general and administrative		7,485			7,917			9,180
		$	10,544		$	12,281		$	14,388
Black-Scholes Valuation Assumptions to Estimates Fair Value of Stock Options and Stock Purchase Rights	'
	The calculation of the Black-Scholes valuations used the following weighted-average assumptions:
		Year Ended December 31,
		2013		2012	2011
	Dividend yield	0%		0%	0%
	Volatility for options	0.82		0.81	0.77
	Volatility for ESPP	0.59		0.65	0.73
	Weighted-average expected life of options (years)	5.25		5.09	5.34
	Weighted-average expected life of ESPP rights (years)	0.5		0.5	0.5
	Risk-free interest rate for options	0.70-1.60%		0.62-1.02%	0.90-2.26%
	Risk-free interest rate for ESPP rights	0.07-0.17%		0.07-0.27%	0.07-0.19%
Net Loss Per Share	'
		Year Ended December 31,
		2013			2012			2011
		(In thousands, except
		per share amounts)
	Numerator:
	Net loss	$	(85,883	)	$	(30,814	)	$	(33,380	)
	Denominator:
	Weighted-average common shares outstanding		47,545			39,434			35,400
	Basic and diluted net loss per share	$	(1.81	)	$	(0.78	)	$	(0.94	)
	Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
	Restricted stock units and options to purchase common stock		6,824			6,339			5,903
	Warrants outstanding		283			283			305
			7,107			6,622			6,208

Collaboration_Agreements_Table

Collaboration Agreements (Tables)	12 Months Ended
	Dec. 31, 2013
Revenue from Collaboration Agreement	'
	The following table presents the Company’s total revenues that have been recognized pursuant to its current collaboration agreement with Astellas and its terminated collaboration agreement with GSK (in thousands):
		Year Ended December 31,
		2013		2012		2011
	Astellas	$	1,537	$	11,624	$	8,515
	GSK		—		10,000		35,000
		$	1,537	$	21,624	$	43,515

Acquisitions_and_AcquisitionRe1

Acquisitions and Acquisition-Related Items (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Value of Net Identified Assets Acquired and Consideration Exchanged	'
	The following table summarizes the fair value of consideration exchanged as part of the termination and transition agreement (in thousands):
	Cash payable to GSK (recorded as “Other noncurrent liability” on the Company’s Balance Sheet for the year ended December 31, 2012)	$	2,314
	Issuance of common shares to GSK		30,268
	Cash received for common shares issued to GSK		(40,000	)
	Settlement of litigation with GSK		20,499
	Transaction costs		476
		$	13,557
Assets acquired (Detail)	'
	Assets acquired as a result of this transaction were as follows (in thousands):
	Inventories	$	11,733
	Manufacturing property and equipment		1,967
	Total assets acquired	$	13,700
Proforma Consolidated Revenues and Net Loss	'
	The following unaudited supplemental pro forma information summarizes the combined results of operations of the Company and the HORIZANT business as though the acquisition had occurred on January 1, 2012 (in thousands):
		Year Ended December 31,
		2013			2012
	Revenues	$	9,128		$	28,119
	Net loss	$	92,791		$	84,695

Cash_and_Cash_Equivalents_Shor1

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments (Tables)	12 Months Ended
	Dec. 31, 2013
Cash and Cash Equivalents, Short-Term Investments and Restricted Investments	'
	The following are summaries of cash and cash equivalents, short-term investments and restricted investments (in thousands):
		Cost		Gross		Gross			Estimated
				Unrealized		Unrealized			Fair
				Gains		Losses			Value
	As of December 31, 2013:
	Cash	$	2,281	$	—	$	—		$	2,281
	Money market funds		10,046		—		—			10,046
	U.S. government-sponsored agencies		2,500		—		—			2,500
	Corporate debt securities		43,831		6		(6	)		43,831
	Certificates of deposit		1,725		—		—			1,725
		$	60,383	$	6	$	(6	)	$	60,383
	Reported as:
	Cash and cash equivalents								$	20,584
	Short-term investments									38,074
	Restricted investments									1,725
									$	60,383
		Cost		Gross		Gross			Estimated
				Unrealized		Unrealized			Fair
				Gains		Losses			Value
	As of December 31, 2012:
	Cash	$	915	$	—	$	—		$	915
	Money market funds		20,897		—		—			20,897
	U.S. government-sponsored agencies		11,329		1		—			11,330
	Corporate debt securities		105,839		32		(11	)		105,860
	Certificates of deposit		1,955		—		—			1,955
		$	140,935	$	33	$	(11	)	$	140,957
	Reported as:
	Cash and cash equivalents								$	36,134
	Short-term investments									102,868
	Restricted investments									1,955
									$	140,957
Available-For-Sale Investments Measured at Fair Value	'
	The Company’s available-for-sale investments, which include cash equivalents and short-term investments, are measured at fair value on a recurring basis and are classified at the following fair value hierarchy (see Note 1 for the Company’s accounting policy on measuring fair value of financial instruments) (in thousands):
				Fair Value Measurements at Reporting Date Using
	Description	Total As of		Quoted Prices in		Significant			Significant
		December 31,		Active Markets		Other			Unobservable
		2013		for Identical		Observable			Inputs
				Assets		Inputs			(Level 3)
				(Level 1)		(Level 2)
	Money market funds	$	10,046	$	10,046	$	—		$	—
	U.S. government-sponsored agencies		2,500		—		2,500			—
	Corporate debt securities		43,831		—		43,831			—
	Certificates of deposit		1,725		—		1,725
	Total	$	58,102	$	10,046	$	48,056		$	—
				Fair Value Measurements at Reporting Date Using
	Description	Total As of		Quoted Prices in		Significant			Significant
		December 31,		Active Markets		Other			Unobservable
		2012		for Identical		Observable			Inputs
				Assets		Inputs			(Level 3)
				(Level 1)		(Level 2)
	Money market funds	$	20,897	$	20,897	$	—		$	—
	U.S. government-sponsored agencies		11,330		—		11,330			—
	Corporate debt securities		105,860		—		105,860			—
	Certificates of deposit		1,955		—		1,955			—
	Total	$	140,042	$	20,897	$	119,145		$	—

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property and Equipment	'
	Property and equipment consisted of the following (in thousands):
		December 31,
		2013			2012
	Laboratory equipment	$	10,701		$	11,478
	Manufacturing property and equipment		1,967			—
	Furniture and fixtures		1,107			1,283
	Computer equipment and software		5,475			5,679
	Leasehold improvements		3,344			4,596
	Construction in-progress		—			104
			22,594			23,140
	Less: Accumulated depreciation and amortization		(20,042	)		(21,612	)
	Property and equipment, net	$	2,552		$	1,528

Other_Accrued_Liabilities_Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2013
Other Accrued Liabilities	'
	Other accrued liabilities at December 31, 2013 and December 31, 2012 were as follows (in thousands):
		December 31,		December 31,
		2013		2012
	Accrued product costs	$	1,903	$	—
	Accrued selling and marketing expenses		883		276
	Accrued general and administrative expenses		632		1,047
	Other liabilities		520		101
	Total other accrued liabilities	$	3,938	$	1,424

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Future Minimum Payments under The Company's Non-Cancelable Operating Lease	'
	At December 31, 2013, future minimum payments under the Company’s non-cancelable operating lease were as follows (in thousands):
	Year ending December 31:
	2014	$	2,127
	2015		1,553
	Total minimum lease payments	$	3,680

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2013
Option activity	'
	A summary of option activity as of and for the year ended December 31, 2013 is presented below:
		Shares			Weighted-		Weighted-		Aggregate
					Average		Average		Intrinsic
					Exercise		Remaining		Value
					Price		Contractual
							Term
									(In thousands)
	Outstanding at January 1, 2013		4,460,348		$	19.19
	Options granted		1,198,500		$	7.91
	Options cancelled		(199,706	)	$	22.61
	Options exercised		(90,178	)	$	3.45
	Outstanding at December 31, 2013		5,368,964		$	16.81		5.81	$	(989,933	)
	Exercisable at December 31, 2013		3,968,914		$	20.1		4.81	$	(644,975	)
Restricted Stock and Performance Stock Unit Activity	'
	A summary of restricted stock and performance stock unit activity for the year ended December 31, 2013 is presented below:
		Shares			Weighted-
					Average
					Grant Date
					Fair Value
	Outstanding at January 1, 2013		1,878,424		$	7.25
	Awards granted		681,500		$	8.13
	Awards cancelled		(302,662	)	$	10.95
	Awards vested		(802,072	)	$	7.73
	Outstanding at December 31, 2013		1,455,190		$	7.15

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Significant Components of Net Deferred Tax Assets	'
	Significant components of the Company’s net deferred tax assets were as follows (in thousands):
		December 31,
		2013			2012
	Net operating loss carryforwards	$	161,663		$	130,104
	Research credit carryforwards		30,111			29,847
	Capitalized research and development		5,579			7,638
	Deferred revenue		4,700			4,994
	Stock options		14,672			15,881
	Other		1,605			2,656
	Total net deferred tax assets		218,330			191,120
	Valuation allowance		(218,330	)		(191,120	)
	Net deferred tax assets	$	—		$	—
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	'
	A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
	January 1, 2013	$	—
	Increases related to current year tax positions		1,340,000
	December 31, 2013	$	1,340,000

Quarterly_Financial_Data_Unaud1

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Data	'
	The following table summarizes the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share data):
		Quarter Ended
		Dec. 31,			Sept. 30,			June 30,			March 31,			Dec. 31,		Sept. 30,			June 30,			March 31,
		2013			2013			2013			2013			2012 (1)		2012			2012			2012
	Selected Quarterly Data:
	Total revenues	$	2,879		$	2,527		$	2,086		$	459		$	487	$	379		$	10,379		$	10,379
	Net income (loss)	$	(19,138	)	$	(18,816	)	$	(24,381	)	$	(23,548	)	$	3,042	$	(16,753	)	$	(7,959	)	$	(9,144	)
	Basic and diluted net income (loss) per share	$	(0.40	)	$	(0.39	)	$	(0.51	)	$	(0.50	)	$	0.07	$	(0.41	)	$	(0.22	)	$	(0.26	)
	(1) The termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the Company and GSK and effectively settled a preexisting relationship (see Note 1 for more information). As a result, the Company recorded a gain on the settlement of litigation (see Note 3 for more information).

Organization_and_Summary_of_Si3

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)

0 Months Ended

1 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

Nov. 08, 2012

Nov. 09, 2012

Oct. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2006

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Jan. 29, 2014

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Nov. 08, 2012

Nov. 09, 2012

D

D

Segment

Nonretirement Postemployment Benefits

Computer Equipment

Certificates of deposit

Certificates of deposit

Deposits on Leased Facilities

Deposits on Leased Facilities

Sales Revenue, Net

Sales Revenue, Net

Sales Revenue, Net

Sales Revenue, Net

Accounts Receivable

Accounts Receivable

Accounts Receivable

Accounts Receivable

Subsequent Event

Maximum

Maximum

Minimum

Glaxo Group Limited

Glaxo Group Limited

Distributor

Wholesale Distributor One

Wholesale Distributor Two

Wholesale Distributor Three

Customer

Wholesale Distributor One

Wholesale Distributor Two

Wholesale Distributor Three

Underwritten Public Offering

Furniture, Fixtures and Equipment

Furniture, Fixtures and Equipment

Organization And Summary Of Significant Accounting Policies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Annual payment for inventory of gabapentin enacarbil in GSK's possession for six years beginning in 2016

'

'

'

$1,000,000

$1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceed from issuance of common stock

40,000,000

'

'

'

30,268,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

20,000,000

20,000,000

Common stock issued in underwritten public offering

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12,000,000

'

'

'

1,841,112

2,190,100

Stock issued, price per-shares

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$10.86

$9.13

Percentage of stock issue price over average stock closing price

12.50%

12.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common Stock Trading Days to be Considered For Valuation

'

10

10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maturity period of highly liquid investments classified as cash equivalents

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'90 days

'

'

'

'

Restricted investments

'

'

'

1,500,000

1,705,000

'

'

'

225,000

250,000

1,500,000

1,705,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letter of credit pledged

'

'

'

225,000

'

1,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of operating segment

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Low risk debt securities, maturity period

'

'

'

'18 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of wholesale distributors

'

'

'

'

'

'

'

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of product shipments represented by wholesale distributors

'

'

'

'

'

'

'

'

'

'

'

'

'

47.00%

33.00%

16.00%

'

'

'

'

'

'

'

'

'

'

Number of customers

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

Percentage of product sales related accounts receivable

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

45.00%

29.00%

22.00%

'

'

'

'

'

'

Accounts receivable, net

'

'

'

939,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property and equipment estimated useful lives

'

'

'

'

'

'

'

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 years

'5 years

'

'

Cash discount offers to customers

'

'

'

2.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Severance benefits charges

'

'

'

'

'

'

703,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Advertising expenses

'

'

'

$8,244,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock price

'

'

'

$5.75

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$6

'

'

'

'

'

Inventory_Detail

Inventory (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Inventory [Line Items]	'
Raw materials	$10,258
Work in progress	76
Finished goods	1,113
Total inventory	11,447
Less: Long-term inventories	10,185
Total inventory classified as current	$1,262

StockBased_Compensation_by_Typ

Stock-Based Compensation by Type of Award (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$10,544	$12,281	$14,388
Effect on basic and diluted net loss per share	($0.22)	($0.31)	($0.41)
Employee Stock Option	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	10,083	11,956	14,044
Employee Stock	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$461	$325	$344

Employee_NonCash_StockBased_Co

Employee Non-Cash Stock-Based Compensation (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Non-cash stock-based compensation	$10,544	$12,281	$14,388
Research and development	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Non-cash stock-based compensation	3,059	4,364	5,208
Selling, general and administrative	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Non-cash stock-based compensation	$7,485	$7,917	$9,180

BlackScholes_Valuation_Assumpt

Black-Scholes Valuation Assumptions to Estimates Fair Value of Stock Options and Stock Purchase Rights (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Dividend yield	0.00%	0.00%	0.00%
Employee Stock Option	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Volatility rate	0.82%	0.81%	0.77%
Weighted-average expected life	'5 years 3 months	'5 years 1 month 2 days	'5 years 4 months 2 days
Risk-free interest rate, minimum	0.70%	0.62%	0.90%
Risk-free interest rate, maximum	1.60%	1.02%	2.26%
Employee Stock	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Volatility rate	0.59%	0.65%	0.73%
Weighted-average expected life	'6 months	'6 months	'6 months
Risk-free interest rate, minimum	0.07%	0.07%	0.07%
Risk-free interest rate, maximum	0.17%	0.27%	0.19%

Net_Loss_Per_Share_Detail

Net Loss Per Share (Detail) (USD $)

3 Months Ended

12 Months Ended

In Thousands, except Per Share data, unless otherwise specified

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Numerator:

'

'

'

'

'

'

'

'

'

'

'

Net loss

($19,138)

($18,816)

($24,381)

($23,548)

$3,042

[1]

($16,753)

($7,959)

($9,144)

($85,883)

($30,814)

($33,380)

Denominator:

'

'

'

'

'

'

'

'

'

'

'

Weighted-average common shares outstanding

'

'

'

'

'

'

'

'

47,545

39,434

35,400

Basic and diluted net loss per share

($0.40)

($0.39)

($0.51)

($0.50)

$0.07

[1]

($0.41)

($0.22)

($0.26)

($1.81)

($0.78)

($0.94)

Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:

'

'

'

'

'

'

'

'

'

'

'

Outstanding securities not included in the computation of diluted net loss per share

'

'

'

'

'

'

'

'

7,107

6,622

6,208

Restricted stock units and options to purchase common stock

'

'

'

'

'

'

'

'

'

'

'

Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:

'

'

'

'

'

'

'

'

'

'

'

Outstanding securities not included in the computation of diluted net loss per share

'

'

'

'

'

'

'

'

6,824

6,339

5,903

Warrants outstanding

'

'

'

'

'

'

'

'

'

'

'

Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:

'

'

'

'

'

'

'

'

'

'

'

Outstanding securities not included in the computation of diluted net loss per share

'

'

'

'

'

'

'

'

283

283

305

[1]

The termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the Company and GSK and effectively settled a preexisting relationship (see Note 1 for more information). As a result, the Company recorded a gain on the settlement of litigation (see Note 3 for more information).

Collaboration_Agreement_Additi

Collaboration Agreement - Additional Information (Detail) (USD $)

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

70 Months Ended

1 Months Ended

64 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2012

Mar. 31, 2007

Mar. 31, 2007

Jun. 30, 2012

Jun. 30, 2012

Glaxo Group Limited

Glaxo Group Limited

Glaxo Group Limited

Licensing Agreements

Licensing Agreements

Licensing Agreements

Licensing Agreements

Licensing Agreements

Licensing Agreements

Licensing Agreements

Exclusive collaboration to develop and commercialize gabapentin enacarbil

Exclusive collaboration to develop and commercialize gabapentin enacarbil

Exclusive collaboration to develop and commercialize gabapentin enacarbil

Exclusive collaboration to develop and commercialize gabapentin enacarbil

Exclusive collaboration to develop and commercialize gabapentin enacarbil

Astellas Pharma Inc.

Astellas Pharma Inc.

Astellas Pharma Inc.

Astellas Pharma Inc.

Astellas Pharma Inc.

Astellas Pharma Inc.

Astellas Pharma Inc.

Glaxo Group Limited

Glaxo Group Limited

Glaxo Group Limited

Glaxo Group Limited

Glaxo Group Limited

Approval of Regnite in Japan

U.S. Food and Drug Administration, or FDA, approval of gabapentin enacarbil

Initial license payment

Initial license payment

Initial license payment

Upon the occurrence of additional clinical and regulatory events

Initial license payment

In connection with the first commercial sale of Horizan

Clinical Trials and Pre-clinical Activities

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenue recognized

$2,879,000

$2,527,000

$2,086,000

$459,000

$487,000

[1]

$379,000

$10,379,000

$10,379,000

$7,951,000

$21,624,000

$43,515,000

'

'

'

'

$52,378,000

$10,000,000

$7,000,000

$1,137,000

$1,515,000

$1,515,000

$205,000,000

'

'

$10,000,000

$85,000,000

Royalty revenue

'

'

'

'

'

'

'

'

400,000

109,000

'

'

'

'

109,000

400,000

'

'

'

'

'

'

'

'

'

'

Deferred revenue

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13,131,000

'

'

'

'

'

'

'

'

'

'

Deferred revenue, current

1,134,000

'

'

'

1,515,000

'

'

'

1,134,000

1,515,000

'

'

'

'

'

1,134,000

'

'

'

'

'

'

'

'

'

'

Deferred revenue, non-current

11,997,000

'

'

'

12,753,000

'

'

'

11,997,000

12,753,000

'

'

'

'

'

11,997,000

'

'

'

'

'

'

'

'

'

'

Deferred revenue, initial up-front license payment received

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

75,000,000

'

'

Payments, maximum amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

130,000,000

'

'

'

Net revenue from unconsolidated joint operating activities

'

'

'

'

'

'

'

'

'

$10,000,000

$35,000,000

$0

$10,000,000

$35,000,000

'

'

'

'

'

'

'

'

'

'

'

'

[1]

The termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the Company and GSK and effectively settled a preexisting relationship (see Note 1 for more information). As a result, the Company recorded a gain on the settlement of litigation (see Note 3 for more information).

Total_Revenues_Recognized_Purs

Total Revenues Recognized Pursuant to Current Collaboration Agreements (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'
Collaboration revenue	$1,137,000	$11,515,000	$8,515,000
Net revenue from unconsolidated joint operating activities	'	10,000,000	35,000,000
Total revenues	1,537,000	21,624,000	43,515,000
Astellas Pharma Inc.	'	'	'
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'
Collaboration revenue	1,537,000	11,624,000	8,515,000
Glaxo Group Limited	'	'	'
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'	'
Net revenue from unconsolidated joint operating activities	$0	$10,000,000	$35,000,000

Acquisitions_and_Acquisition_R

Acquisitions and Acquisition Related items - Additional information (Detail) (USD $)	0 Months Ended		1 Months Ended	12 Months Ended
	Nov. 08, 2012	Nov. 09, 2012	Oct. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
		D	D
Business Acquisition [Line Items]	'	'	'	'	'
Proceed from issuance of common stock	$40,000,000	'	'	'	$30,268,000
Percentage of stock issue price over average stock closing price	12.50%	12.50%	'	'	'
Common Stock Trading Days to be Considered For Valuation	'	10	10	'	'
Annual payment for inventory of gabapentin enacarbil in GSK's possession for six years beginning in 2016	'	'	'	1,000,000	1,000,000
Horizant Business	'	'	'	'	'
Business Acquisition [Line Items]	'	'	'	'	'
Transaction costs	'	'	'	476,000	'
Revenues	'	'	'	6,414,000	'
Net loss	'	'	'	-21,522,000	'
Glaxo Group Limited	'	'	'	'	'
Business Acquisition [Line Items]	'	'	'	'	'
Proceed from issuance of common stock	$20,000,000	20,000,000	'	'	'
Stock issued, shares	1,841,112	2,190,100	'	'	'
Stock issued, price per-shares	$10.86	9.132	'	'	'

Fair_Value_of_Net_Identifiable

Fair Value of Net Identifiable Assets Acquired and Consideration Exchanged (Detail) (USD $)	0 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Nov. 08, 2012	Dec. 31, 2012
Business Acquisition [Line Items]	'	'
Cash payable to GSK (recorded as "Other noncurrent liability" on the Company's balance sheet for the year ended December 31, 2012)	$2,314	'
Issuance of common shares to GSK	30,268	'
Cash received for common shares issued to GSK	-40,000	-30,268
Settlement of litigation with GSK	20,499	'
Transaction costs	476	'
Consideration transferred , total	$13,557	'

Assets_Acquired_Detail

Assets Acquired (Detail) (USD $)	Dec. 31, 2013	1-May-13
In Thousands, unless otherwise specified		Horizant Business
Business Acquisition [Line Items]	'	'
Inventories	$11,733	$11,733
Manufacturing property and equipment	1,967	1,967
Total assets acquired	'	$13,700

Proforma_Consolidated_Revenue_

Proforma Consolidated Revenue and Net Loss (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]	'	'
Revenues	$9,128	$28,119
Net loss	$92,791	$84,695

Cash_and_Cash_Equivalents_Shor2

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Cost	$60,383	$140,935
Gross Unrealized Gains	6	33
Gross Unrealized Losses	-6	-11
Estimated Fair Value	60,383	140,957
U.S. government-sponsored agencies	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Cost	2,500	11,329
Gross Unrealized Gains	'	1
Estimated Fair Value	2,500	11,330
Corporate debt securities	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Cost	43,831	105,839
Gross Unrealized Gains	6	32
Gross Unrealized Losses	-6	-11
Estimated Fair Value	43,831	105,860
Certificates of deposit	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Cost	1,725	1,955
Estimated Fair Value	1,725	1,955
Short-term investments	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Estimated Fair Value	38,074	102,868
Restricted investments	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Estimated Fair Value	1,725	1,955
Cash	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Cost	2,281	915
Estimated Fair Value	2,281	915
Money market funds	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Cost	10,046	20,897
Estimated Fair Value	10,046	20,897
Cash and cash equivalents	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'
Estimated Fair Value	$20,584	$36,134

Cash_and_Cash_Equivalents_Shor3

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'	'
Gross realized gains or losses recognized	$0	$0	$0
Amounts reclassified out of accumulated other comprehensive income to earnings	$0	$0	$0
Maximum	'	'	'
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]	'	'	'
Contractual maturities of investments held	'1 year	'1 year	'

AvailableForSale_Investments_M

Available-For-Sale Investments Measured at Fair Value (Detail) (Fair Value Measurements, Recurring basis, USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	$58,102	$140,042
Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	10,046	20,897
U.S. government-sponsored agencies	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	2,500	11,330
Corporate debt securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	43,831	105,860
Certificates of deposit	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	1,725	1,955
Quoted Prices in Active Markets for Identical Assets (Level 1)	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	10,046	20,897
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	10,046	20,897
Significant Other Observable Inputs (Level 2)	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	48,056	119,145
Significant Other Observable Inputs (Level 2) | U.S. government-sponsored agencies	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	2,500	11,330
Significant Other Observable Inputs (Level 2) | Corporate debt securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	43,831	105,860
Significant Other Observable Inputs (Level 2) | Certificates of deposit	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Available-for-sale investments	$1,725	$1,955

Property_and_Equipment_Detail

Property and Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Laboratory equipment	$10,701	$11,478
Manufacturing property and equipment	1,967	'
Furniture and fixtures	1,107	1,283
Computer equipment and software	5,475	5,679
Leasehold improvements	3,344	4,596
Construction in-progress	'	104
Property, Plant and Equipment, Gross, Total	22,594	23,140
Less: Accumulated depreciation and amortization	-20,042	-21,612
Property and equipment, net	$2,552	$1,528

Other_Accrued_Liabilities_Deta

Other Accrued Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Other Accrued Liabilities [Line Items]	'	'
Accrued product costs	$1,903	'
Accrued selling and marketing expenses	883	276
Accrued general and administrative expenses	632	1,047
Other liabilities	520	101
Total other accrued liabilities	$3,938	$1,424

Restructuring_Additional_Infor

Restructuring - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Restructuring Cost and Reserve [Line Items]	'	'
Restructuring charges	'	$2,923,000
Cash payments	1,737,000	'
Accrued restructuring charges, current	993,000	'
Facility	'	'
Restructuring Cost and Reserve [Line Items]	'	'
Restructuring charges	'	2,476,000
Property and Equipment	'	'
Restructuring Cost and Reserve [Line Items]	'	'
Restructuring charges	'	$447,000

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended
	Oct. 31, 2012	Feb. 29, 2008	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2006
Commitments and Contingencies Disclosure [Line Items]	'	'	'	'	'	'
Extended lease term	'2 years	'	'	'	'	'
Lease commencement date	'	'2001-12	'	'	'	'
Letter of credit pledged	'	'	$225,000	'	'	$1,500,000
Restricted investments	'	'	1,500,000	1,705,000	'	'
Rent expense, excluding rent expense recognized as part of restructuring charges	'	'	2,626,000	3,185,000	4,347,000	'
Net deferred rent asset	'	'	477,000	720,000	'	'
Deferred rent asset, current	'	'	308,000	243,000	'	'
Deferred rent asset, noncurrent	'	'	$169,000	$477,000	'	'
Second Amendment	'	'	'	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'	'	'	'
Lease expiration date	27-Aug-15	'	'	'	'	'
3400 Central Expressway, Santa Clara, California	'	'	'	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'	'	'	'
Operating lease, area of office space	'	59,000	'	'	'	'
Operating lease, lease expiration year	'	'2013-08	'	'	'	'
Operating lease, lease term	'	'60 months	'	'	'	'
3410 Central Expressway, Santa Clara, California | First Amendment	'	'	'	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'	'	'	'
Operating lease, lease expiration year	'	'2013-08	'	'	'	'
Extended lease term	'	'2 years	'	'	'	'

Future_Minimum_Payments_under_

Future Minimum Payments under The Company's Non-Cancelable Operating Lease (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Operating Leases [Line Items]	'
2014	$2,127
2015	1,553
Total minimum lease payments	$3,680

Stockholders_Equity_Additional

Stockholders Equity - Additional Information (Detail) (USD $)

12 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

0 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Jan. 31, 2005

Jan. 31, 2005

Jan. 31, 2005

31-May-10

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

31-May-10

31-May-10

Dec. 31, 2013

Dec. 31, 2012

31-May-10

31-May-10

Jan. 31, 2007

Jan. 31, 2007

31-May-08

31-May-08

31-May-10

31-May-10

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

31-May-10

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

31-May-12

Jan. 31, 2005

31-May-12

Jan. 31, 2005

Jan. 31, 2005

Dec. 16, 2005

Dec. 16, 2005

Dec. 16, 2005

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Employee Stock

Employee Stock

Employee Stock

Employee Stock

Warrants outstanding

Warrants outstanding

Restricted Stock Units And Performance Stock Unit Awards

Restricted Stock Units And Performance Stock Unit Awards

Restricted Stock Units And Performance Stock Unit Awards

Stock Incentive Plan 1999

Stock Incentive Plan 1999

Stock Incentive Plan 1999

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

2005 Stock Incentive Plan

New Employee Inducement Stock Awards

New Employee Inducement Stock Awards

2010 Inducement Plan

2010 Inducement Plan

2010 Inducement Plan

2010 Inducement Plan

2010 Inducement Plan

2010 Inducement Plan

2010 Inducement Plan

2005 Non-Employee Directors Stock Option Plan

2005 Non-Employee Directors Stock Option Plan

2005 Non-Employee Directors Stock Option Plan

2005 Non-Employee Directors Stock Option Plan

2005 Non-Employee Directors Stock Option Plan

2005 Non-Employee Directors Stock Option Plan

2005 Non-Employee Directors Stock Option Plan

Stockholder Rights Plan

Stockholder Rights Plan

Stockholder Rights Plan

Maximum

Exercisable at $15.00 per share

Maximum

Stock Option

Maximum

Stock Option

Performance Stock Units

Performance Stock Units

Performance Stock Units

Performance Stock Units

Performance Stock Units

Performance Stock Units

Performance Stock Units

Stock purchase rights, stock bonus rights, stock appreciation rights

Stock purchase rights, stock bonus rights, stock appreciation rights

Stock purchase rights, stock bonus rights, stock appreciation rights

Stock purchase rights, stock bonus rights, stock appreciation rights

Restricted Stock Units (RSUs)

Restricted Stock Units (RSUs)

Nonqualified Stock Options

Restricted Stock Units (RSUs)

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Stock Option

Series A Junior Participating Preferred Stock

Minimum

Maximum

Minimum

Maximum

Vesting Scenario One

Vesting Scenario Two

Maximum

Maximum

Initial Grant

Initial Grant

On Date Of Annual Meeting Of Shareholders

On Date Of Annual Meeting Of Shareholders

Maximum

Stockholders Equity Note [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares authorized

100,000,000

100,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Acquisition percentage of common stock to triggers exercise of preferred stock rights

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

15.00%

Tender offer percentage of common stock to trigger exercise of preferred stock right

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

15.00%

Stockholders' rights plan, expiration date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13-Jan-16

'

'

Equity Incentive Plans, weighted average exercise price

$7.91

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$42.59

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$140

'

Equity Incentive Plans, exercise prices as a percentage of fair value of common stock

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

85.00%

'

'

85.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, annual vesting percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

25.00%

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, vesting period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'4 years

'

'

'4 years

'3 years

'

'

'

'

'

'

'

'

'

'

'4 years

'3 years

'4 years

'4 years

'

'4 years

'

'

'

'

'

'

'

'24 months

'4 years

'12 months

'12 months

'

'

'

'

Equity Incentive Plans, option expiration period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 years

'

'

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 years

'

'

'

'

'

'

'10 years

'

'

'

'

'

'

'

'10 years

'

'

'

Equity Incentive Plans, vesting percentage in year one

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, annual vesting percentage in year two

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, annual vesting percentage in year three

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, common stock subject to issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200.00%

0.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, granted

'

'

'

'

'

'

142,455

185,249

'

'

'

'

681,500

'

'

'

'

'

'

'

'

140,000

'

'

'

'

'

'

'

'

'

'

'

'

'

10,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, granted date fair value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$2,675,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, cancelled

'

'

'

'

'

'

'

'

'

'

'

'

302,662

'

'

'

'

'

'

'

'

'

97,300

'

'

40,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock-based compensation expense

10,544,000

12,281,000

14,388,000

'

'

'

461,000

325,000

344,000

'

'

'

'

'

'

'

'

'

'

'

'

'

232,000

638,000

636,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, shares authorized for issuance

'

'

'

'

'

'

'

'

'

1,195,555

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,000,000

'

'

'

'

'

'

350,000

'

'

'

'

975,000

'

'

'

'

'

'

150,000

'

'

'

Equity Incentive Plans, annual increase in shares issuable as a percentage of common shares outstanding

'

'

'

'

'

'

'

'

'

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, annual increase in number of shares issuable

'

'

'

'

'

'

'

'

'

250,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, additional shares authorized for issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,176,691

'

'

'

'

'

'

'

'

'

625,000

'

'

'

'

135,000

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, shares available for future grant

'

'

'

'

'

'

255,602

148,057

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,810,768

1,208,954

'

'

'

'

'

'

'

'

'

365,686

752,901

'

'

30,000

15,000

'

'

'

'

'

'

'

'

Equity Incentive Plans, granted

1,198,500

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

140,612

'

'

'

'

'

'

'

'

'

'

30,000

25,000

15,000

10,000

'

'

'

'

Equity Incentive Plans, vesting percentage on first anniversary

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Incentive Plans, monthly vesting rate

'

'

'

'

'

'

'

'

'

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'

'1/48

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Closing stock price

$5.75

'

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'

'

'

'

'

Equity Incentive Plans, weighted-average grant date fair values of options granted

$5.22

$3.12

$5.26

'

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'

Equity Incentive Plans, weighted-average grant date fair values

'

'

'

'

'

'

'

'

'

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'

'

$8.13

$5.22

$9.04

'

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'

Equity Incentive Plans, total intrinsic value of options exercised

304,000

137,000

20,000

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'

Equity Incentive Plans, total fair value of restricted stock units vested

'

'

'

6,202,053

4,372,000

3,406,000

'

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'

Equity Incentive Plans, unvested options

1,400,050

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'

Equity Incentive Plans, unvested awards

1,455,190

'

'

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'

'

'

'

1,455,190

1,878,424

'

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'

Equity Incentive Plans, total compensation cost not yet recognized

$12,279,000

'

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Equity Incentive Plans, estimated weighted-average amortization period

'2 years 4 months 13 days

'

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Warrants outstanding

'

'

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'

283,420

283,420

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Warrants exercise price

'

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'

25.4

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'

Option_activity_Detail

Option activity (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013
Shares	'
Outstanding at January 1, 2013	4,460,348
Options granted	1,198,500
Options cancelled	-199,706
Options exercised	-90,178
Outstanding at December 31, 2013	5,368,964
Exercisable at December 31, 2013	3,968,914
Weighted-Average Exercise Price	'
Outstanding at January 1, 2013	$19.19
Options granted	$7.91
Options cancelled	$22.61
Options exercised	$3.45
Outstanding at December 31, 2013	$16.81
Exercisable at December 31, 2013	$20.10
Weighted-Average Remaining Contractual Term	'
Outstanding at December 31, 2013	'5 years 9 months 22 days
Exercisable at December 31, 2013	'4 years 9 months 22 days
Aggregate Intrinsic Value	'
Outstanding at December 31, 2013	($989,933)
Exercisable at December 31, 2013	($644,975)

Restricted_Stock_and_Performan

Restricted Stock and Performance Stock Unit Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Shares	'	'	'
Outstanding at December 31, 2013	1,455,190	'	'
Restricted Stock Units And Performance Stock Unit Awards	'	'	'
Shares	'	'	'
Outstanding at January 1, 2013	1,878,424	'	'
Awards granted	681,500	'	'
Awards cancelled	-302,662	'	'
Awards vested	-802,072	'	'
Outstanding at December 31, 2013	1,455,190	1,878,424	'
Weighted-Average Grant Date Fair Value	'	'	'
Outstanding at January 1, 2013	$7.25	'	'
Awards granted	$8.13	$5.22	$9.04
Awards cancelled	$10.95	'	'
Awards vested	$7.73	'	'
Outstanding at December 31, 2013	$7.15	$7.25	'

Preferred_Stock_Additional_Inf

Preferred Stock - Additional Information (Detail)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Class of Stock [Line Items]	'	'
Preferred stock, shares authorized	5,000	5,000
Series A Junior Participating Preferred Stock	'	'
Class of Stock [Line Items]	'	'
Preferred stock, shares authorized	1,000	1,000

Significant_Components_of_Net_

Significant Components of Net Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Deferred Tax Assets and Liabilities [Line Items]	'	'
Net operating loss carryforwards	$161,663	$130,104
Research credit carryforwards	30,111	29,847
Capitalized research and development	5,579	7,638
Deferred revenue	4,700	4,994
Stock options	14,672	15,881
Other	1,605	2,656
Total net deferred tax assets	218,330	191,120
Valuation allowance	-218,330	-191,120
Net deferred tax assets	'	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Line Items]	'	'	'
Increase in valuation allowance	$27,210,000	$6,259,000	$12,301,000
Valuation allowance	218,330,000	191,120,000	'
Valuation allowance related to stock option	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Valuation allowance	529,000	'	'
Federal	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carryforwards	414,870,000	'	'
Research and development tax credit	23,177,000	'	'
Federal | Expiration Beginning Year	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carryforwards, expiration year	'2022	'	'
Research and development tax credit, expiration year	'2021	'	'
Federal | Expiration Ending Year	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carryforwards, expiration year	'2033	'	'
Research and development tax credit, expiration year	'2033	'	'
State	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carryforwards	308,758,000	'	'
State | Expiration Beginning Year	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carryforwards, expiration year	'2014	'	'
State | Expiration Ending Year	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carryforwards, expiration year	'2033	'	'
State | Do Not Expire	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Research and development tax credit	$12,009,000	'	'

Reconciliation_of_Beginning_an

Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Income Tax Contingency [Line Items]	'
Increases related to current year tax positions	$1,340,000
Ending balance	$1,340,000

RelatedParty_Transaction_Addit

Related-Party Transaction - Additional Information (Detail) (Jon R. Duane a director of McKinsey & Company Inc, USD $)	8 Months Ended
	Dec. 31, 2011
Jon R. Duane a director of McKinsey & Company Inc	'
Related Party Transaction [Line Items]	'
Related party transaction, expense incurred	$1,011,000

Quarterly_Financial_Data_Detai

Quarterly Financial Data (Detail) (USD $)	3 Months Ended									12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information [Line Items]	'	'	'	'	'		'	'	'	'	'	'
Total revenues	$2,879	$2,527	$2,086	$459	$487	[1]	$379	$10,379	$10,379	$7,951	$21,624	$43,515
Net income (loss)	($19,138)	($18,816)	($24,381)	($23,548)	$3,042	[1]	($16,753)	($7,959)	($9,144)	($85,883)	($30,814)	($33,380)
Basic and diluted net income (loss) per share	($0.40)	($0.39)	($0.51)	($0.50)	$0.07	[1]	($0.41)	($0.22)	($0.26)	($1.81)	($0.78)	($0.94)
[1]	The termination and transition agreement provided for a mutual release of claims and resolved all ongoing litigation between the Company and GSK and effectively settled a preexisting relationship (see Note 1 for more information). As a result, the Company recorded a gain on the settlement of litigation (see Note 3 for more information).

Subsequent_Event_Additional_In

Subsequent Event - Additional Information (Detail) (USD $)	Dec. 31, 2013	Jan. 29, 2014	Feb. 21, 2014
		Subsequent Event	Subsequent Event
		Underwritten Public Offering	Underwriters Exercised in full Over-allotment Option
Subsequent Event [Line Items]	'	'	'
Common stock issued in underwritten public offering	'	12,000,000	1,800,000
Common stock price	$5.75	$6	'
Net cash proceeds from shares offering	'	$67,300,000	$10,100,000