Athersys, Inc / New (ATHXQ) 10-K 13 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Mar. 01, 2014	Jun. 28, 2013
Document And Entity Information [Abstract]	'	'	'
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	'ATHX	'	'
Entity Registrant Name	'ATHERSYS, INC / NEW	'	'
Entity Central Index Key	'0001368148	'	'
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	'	76,633,698	'
Entity Public Float	'	'	$89.40

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$31,948	$25,533
Accounts receivable	520	490
Prepaid expenses and other	387	286
Total current assets	32,855	26,309
Equipment, net	1,333	1,294
Total assets	34,188	27,603
Current liabilities:	'	'
Accounts payable	2,243	1,767
Accrued compensation and related benefits	1,067	827
Accrued clinical trial costs	88	950
Accrued expenses	884	934
Deferred revenue	86	'
Total current liabilities	4,368	4,478
Note payable	176	169
Warrant liabilities	9,823	2,709
Stockholders' equity:	'	'
Preferred stock, at stated value; 10,000,000 shares authorized, and no shares issued and outstanding at December 31, 2013 and December 31, 2012	'	'
Common stock, $0.001 par value; 150,000,000 and 100,000,000 shares authorized at December 31, 2013 and December 31, 2012, respectively, 70,749,212 and 53,058,632 shares issued at December 31, 2013 and December 31, 2012, respectively, and 70,683,480 and 53,058,632 shares outstanding at December 31, 2013 and December 31, 2012, respectively	71	53
Additional paid-in capital	284,323	253,889
Treasury stock, at cost; 65,732 shares at December 31, 2013	-135	'
Accumulated deficit	-264,438	-233,695
Total stockholders' equity	19,821	20,247
Total liabilities and stockholders' equity	$34,188	$27,603

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Statement Of Financial Position [Abstract]	'	'
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	'	'
Preferred stock, shares outstanding	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	150,000,000	100,000,000
Common stock, shares issued	70,749,212	53,058,632
Common stock, shares outstanding	70,683,480	53,058,632
Treasury stock, shares outstanding	65,732	'

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	'	'	'
Contract revenue	$755	$7,380	$9,015
Grant revenue	1,683	1,328	1,329
Total revenues	2,438	8,708	10,344
Costs and expenses	'	'	'
Research and development (including stock compensation expense of $639, $150 and $205 in 2013, 2012 and 2011, respectively)	20,484	19,636	18,930
General and administrative (including stock compensation expense of $884, $331 and $347 in 2013, 2012 and 2011, respectively)	6,065	4,753	4,916
Depreciation	346	320	278
Total costs and expenses	26,895	24,709	24,124
Loss from operations	-24,457	-16,001	-13,780
Other income (expense), net	38	-1,138	-778
(Expense) income from change in fair value of warrants	-6,324	2,404	812
Net loss	-30,743	-14,735	-13,746
Basic and diluted net loss per common share	($0.53)	($0.45)	($0.59)
Weighted average shares outstanding, basic and diluted	57,674,833	32,556,781	23,239,019
Items included in other comprehensive income (loss):	'	'	'
Proportional share of comprehensive (loss) income of equity method investment	'	-28	28
Unrealized loss on available-for-sale securities	'	'	-26
Other comprehensive (loss) income items	'	-28	2
Comprehensive loss	($30,743)	($14,763)	($13,744)

Consolidated_Statements_of_Ope1

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Research and development [Member]	'	'	'
Stock compensation expense	$639	$150	$205
General and administrative [Member]	'	'	'
Stock compensation expense	$884	$331	$347

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity (USD $)	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
In Thousands, except Share data
Beginning balance at Dec. 31, 2010	$9,005	'	$19	$214,174	'	$26	($205,214)
Common stock beginning balance, shares at Dec. 31, 2010	'	'	18,930,678	'	'	'	'
Preferred stock shares, beginning balance at Dec. 31, 2010	'	'	'	'	'	'	'
Stock based compensation	552	'	'	552	'	'	'
Issuance of common stock and warrants, net of issuance costs	11,485	'	5	11,480	'	'	'
Issuance of common stock and warrants, net of issuance costs, Shares	'	'	5,556,582	'	'	'	'
Net loss	-13,746	'	'	'	'	'	-13,746
Other comprehensive income (loss) items	-26	'	'	'	'	2	'
Ending balance at Dec. 31, 2011	7,298	'	24	226,206	'	28	-218,960
Common stock ending balance, shares at Dec. 31, 2011	'	'	24,487,260	'	'	'	'
Preferred stock shares, ending balance at Dec. 31, 2011	'	'	'	'	'	'	'
Stock based compensation	481	'	'	481	'	'	'
Issuance of common stock and warrants, net of issuance costs	27,231	'	29	27,202	'	'	'
Issuance of common stock and warrants, net of issuance costs, Shares	'	'	28,561,553	'	'	'	'
Issuance of common stock under equity compensation plans	'	'	'	'	'	'	'
Issuance of common stock under equity compensation plans, Shares	'	'	9,819	'	'	'	'
Net loss	-14,735	'	'	'	'	'	-14,735
Other comprehensive income (loss) items	'	'	'	'	'	-28	'
Ending balance at Dec. 31, 2012	20,247	'	53	253,889	'	'	-233,695
Common stock ending balance, shares at Dec. 31, 2012	53,058,632	'	53,058,632	'	'	'	'
Preferred stock shares, ending balance at Dec. 31, 2012	'	'	'	'	'	'	'
Stock based compensation	1,523	'	'	1,523	'	'	'
Issuance of common stock from warrant exercises, Cost	797	'	'	797	'	'	'
Issuance of common stock from warrant exercises, Shares	'	'	397,826	'	'	'	'
Issuance of common stock and warrants, net of issuance costs	28,267	'	17	28,113	137	'	'
Issuance of common stock and warrants, net of issuance costs, Shares	10,000,000	'	16,899,999	'	'	'	'
Issuance of common stock under equity compensation plans	-270	'	1	1	-272	'	'
Issuance of common stock under equity compensation plans, Shares	479,490	'	327,023	'	'	'	'
Net loss	-30,743	'	'	'	'	'	-30,743
Other comprehensive income (loss) items	'	'	'	'	'	'	'
Ending balance at Dec. 31, 2013	$19,821	'	$71	$284,323	($135)	'	($264,438)
Common stock ending balance, shares at Dec. 31, 2013	70,683,480	'	70,683,480	'	'	'	'
Preferred stock shares, ending balance at Dec. 31, 2013	'	'	'	'	'	'	'

Consolidated_Statements_of_Cas

Consolidated 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	($30,743)	($14,735)	($13,746)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Depreciation	346	320	278
Realized gain on investments and available-for-sale securities	'	-183	-55
Stock-based compensation	1,523	481	552
Issuance of common stock to former lenders	'	1,005	683
Change in fair value of warrant liabilities	6,324	-2,404	-812
Amortization of premium on available-for-sale securities and other	7	14	58
Changes in operating assets and liabilities:	'	'	'
Accounts receivable	-30	199	1,745
Prepaid expenses and other assets	-101	580	-511
Accounts payable and accrued expenses	-196	198	983
Deferred revenue	86	-3,140	-3,664
Net cash used in operating activities	-22,784	-17,665	-14,489
Investing activities	'	'	'
Purchase of available-for-sale securities	'	'	-12,508
Proceeds from maturities of available-for-sale securities	'	4,237	21,672
Purchases of equipment	-385	-347	-590
Net cash (used in) provided by investing activities	-385	3,890	8,574
Financing activities	'	'	'
Proceeds from note payable	'	166	'
Purchase of treasury stock	-272	'	'
Proceeds from exercise of warrants	402	'	'
Proceeds from issuance of common stock and warrants, net	29,454	30,357	12,595
Net cash provided by financing activities	29,584	30,523	12,595
Increase in cash and cash equivalents	6,415	16,748	6,680
Cash and cash equivalents at beginning of year	25,533	8,785	2,105
Cash and cash equivalents at end of year	$31,948	$25,533	$8,785

Background

Background	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Background	'
	A. Background
	We are an international biopharmaceutical company that is focused primarily in the field of regenerative medicine and operate in one business segment. Our operations consist primarily of research and product development activities.

Accounting_Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Accounting Policies	'
	B. Accounting Policies
	Principles of Consolidation
	The consolidated financial statements include our accounts and results of operations and those of our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Investments in joint ventures are accounted for using the equity method when we do not control the investee, but have the ability to exercise significant influence over the investee’s operations and financial policies. We liquidated our investment in our joint venture in January 2012 and recognized a gain of $183,000.
	Revenue Recognition
	Our license and collaboration agreements may contain multiple elements, including license and technology access fees, research and development funding, manufacturing revenue, cost-sharing, milestones and royalties. The deliverables under such an arrangement are evaluated under Accounting Standards Codification (“ASC”) 605-25, Multiple-Element Arrangements. Effective January 1, 2011, we adopted ASU 2009-13, Multiple-Deliverable Revenue Arrangements (“ASU 2009-13”), which amended the guidance in ASC 605-25 on the accounting for arrangements involving the delivery of more than one element. Pursuant to the new standard, each required deliverable is evaluated to determine whether it qualifies as a separate unit of accounting based on whether the deliverable has “stand-alone value” to the customer. The arrangement’s consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. In general, the consideration allocated to each unit of accounting is recognized as the related goods or services are delivered, limited to the consideration that is not contingent upon future deliverables.
	We adopted this new accounting standard on a prospective basis for agreements containing multiple elements entered into on or after January 1, 2011, and for any agreements entered into prior to January 1, 2011, but materially modified on or after that date.
	The primary impact of adopting the new standard is expected to be the earlier recognition of revenue for multiple element arrangements. The adoption of ASU 2009-13 did not affect revenues that we have earned through December 31, 2013. The impact of adopting this new accounting standard is dependent on the terms and conditions of any future arrangements that we may enter into that include multiple elements and arrangements entered into prior to January 1, 2011 that are materially modified. Depending on the terms of any such arrangements, the adoption of this accounting standard may have a material impact on our consolidated results of operations or financial position as it may have the potential effect of less revenue deferral for new collaborations than we have historically experienced.
	For agreements entered into prior to January 1, 2011 and not materially modified thereafter, we continue to apply our prior accounting policy with respect to such arrangements. Under this policy, the deliverables under the arrangement are evaluated to assess whether they have standalone value and objective and reliable evidence of fair value, and if so, are accounted for as a single unit. We then recognize revenue for each unit based on the culmination of the earnings process under ASC 605-S25, issued as Staff Accounting Bulletin (“SAB”) Topic 13, and our estimated performance period for the single units of accounting based on the specific terms of each collaborative agreement. We subsequently adjust the estimated performance periods, if appropriate, on a prospective basis based upon available facts and circumstances. Future changes in estimates of the performance period may materially impact the timing of future revenue recognized. Amounts received prior to satisfying the revenue recognition criteria for contract revenues are recorded as deferred revenue in the accompanying balance sheets. Reimbursement amounts (other than those accounted for using collaboration accounting) paid to us are recorded on a gross basis in the statements of operations as contract revenues.
	We recognize revenue from at-risk, performance milestones that are substantive in the period that the milestone is achieved, as defined in the respective contracts.
	Also included in contract revenue are license fees received from Bristol-Myers Squibb, which are specifically set forth in the license and collaboration agreement as amounts due to us based on our completion of certain tasks (e.g., delivery and acceptance of a cell line) and development milestones (e.g., clinical trial phases), and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced and recorded as revenue as tasks are completed and as milestones are achieved.
	Similarly, grant revenue consists of funding under cost reimbursement programs primarily from federal and state sources for qualified research and development activities performed by us, and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced (unless prepaid) and recorded as revenue as tasks are completed.
	Cash and Cash Equivalents
	We consider all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents are primarily invested in money market funds and commercial paper. The carrying amount of our cash equivalents approximates fair value due to the short maturity of the investments.
	Research and Development
	Research and development expenditures, which consist primarily of costs associated with external clinical and preclinical study fees, manufacturing costs, salaries and related personnel costs, legal expenses resulting from intellectual property application processes, and laboratory supply and reagent costs, including direct and allocated overhead expenses, are charged to expense as incurred.
	Collaborative Arrangements
	Collaborative arrangements that involve cost or future profit sharing are reviewed to determine the nature of the arrangement and the nature of the collaborative parties’ businesses. The arrangements are also reviewed to determine if one party has sole or primary responsibility for an activity, or whether the parties have shared responsibility for the activity. If responsibility for an activity is shared and there is no principal party, then the related costs of that activity are recognized by us on a net basis in the statement of operations (e.g., total cost less reimbursement from collaborator). If we are deemed to be the principal party for an activity, then the costs and revenues associated with that activity are recognized on a gross basis in the statement of operations. The accounting may be susceptible to change if the nature of a collaborator’s business changes. Our only collaboration accounted for on a net basis was our cost-sharing collaboration with Angiotech Pharmaceuticals, Inc. (“Angiotech”), which was terminated in 2011.
	Clinical Trial Costs
	Clinical trial costs are accrued based on work performed by outside contractors that manage and perform the trials. We obtain initial estimates of total costs based on enrollment of subjects, project management estimates and other activities. Actual costs are typically charged to us and recognized as the tasks are completed by the contractor, and if we are invoiced based on progress payments as opposed to actual costs, we develop estimates of work completed to date. Accrued clinical trial costs may be subject to revisions as clinical trials progress, and any revisions are recorded in the period in which the facts that give rise to the revisions become known.
	Royalties
	We may be required to make future royalty payments to certain parties based on product sales under license agreements. We did not pay any royalties during the three-year period ended December 31, 2013.
	Investments in Available-for-Sale Securities
	We determine the appropriate classification of investment securities at the time of purchase and re-evaluate such designation as of each balance sheet date. Our investments typically consist of United States government obligations and corporate debt securities, which are classified as available-for-sale and are valued based on quoted prices in active markets for identical assets (Level 1). Available-for-sale securities are carried at fair value, with the unrealized gains and losses, net of applicable tax, reported as a component of accumulated other comprehensive income. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization or accretion is included in interest income. Realized gains and losses on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific identification method. Interest earned on securities classified as available-for-sale is included in interest income. None of our financial assets are in markets that are not active.
	Long-Lived Assets
	Equipment is stated at acquired cost less accumulated depreciation. Laboratory and office equipment are depreciated on the straight-line basis over the estimated useful lives (three to ten years). Leasehold improvements are amortized over the shorter of the lease term or estimated useful life.
	Long-lived assets are evaluated for impairment when events or changes in circumstances indicate that the carrying amount of the asset or related group of assets may not be recoverable. If the expected future undiscounted cash flows are less than the carrying amount of the asset, an impairment loss is recognized at that time. Measurement of impairment may be based upon appraisal, market value of similar assets or discounted cash flows.
	Patent Costs and Rights
	Costs of prosecuting and maintaining patents and patent rights are expensed as incurred. As of December 31, 2013, we have filed for broad intellectual property protection on our proprietary technologies. We currently have numerous United States patent applications and corresponding international patent applications related to our technologies, as well as many issued United States and international patents.
	Warrant Liabilities
	We account for common stock warrants as either liabilities or as equity instruments depending on the specific terms of the warrant agreement. Registered common stock warrants that could require cash settlement or liquidated damages are accounted for as liabilities. We classify these warrant liabilities on the consolidated balance sheet as non-current liabilities. The warrant liabilities are revalued at fair value at each balance sheet date subsequent to the initial issuance. We use the Black-Scholes valuation model to value the warrant liabilities at fair value. The fair value is estimated using the expected volatility based on our historical volatility for warrants issued after January 1, 2013, or for warrants issued prior to 2013, using the historical volatilities of comparable companies from a representative peer group selected based on industry and market capitalization. The fair value of the warrants is determined using probability weighted-average assumptions, when appropriate. Changes in the fair market value of the warrant are reflected in the consolidated statement of operations as other income (expense).
	Treasury Stock
	Treasury stock is recorded at cost and any difference between the cost basis and the selling price of treasury stock is recognized as additional paid-in capital. Treasury stock is relieved on a first-in-first-out basis at actual cost. At December 31, 2013, we had 65,732 shares of common stock held in treasury and available for reissuance.
	Comprehensive Income (Loss)
	Unrealized gains and losses on our available-for-sale securities, if any, and the proportional share of comprehensive income and loss of our equity method investment, which was liquidated in 2012, are the only components of accumulated other comprehensive income.
	Concentration of Credit Risk
	Our accounts receivable are generally comprised of amounts due from collaborators and granting authorities and are subject to concentration of credit risk due to the absence of a large number of customers. At December 31, 2013, the majority of our accounts receivable are due from granting authorities. We do not require collateral from these customers.
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
	Stock-Based Compensation
	We recognize stock-based compensation expense on the straight-line method and use a Black-Scholes option-pricing model to estimate the fair value of option awards. The expected term of options granted represent the period of time that option grants are expected to be outstanding. We use the “simplified” method to calculate the expected life of option grants given our limited history of exercise activity and determine volatility by using our historical stock volatility. The fair value of our restricted stock units are equal to the closing price of our common stock on the date of grant and is expensed over the vesting period on a straight-line basis. Estimates of fair value are not intended to predict actual future events or the value ultimately realized by persons that receive equity awards.
	Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. If actual forfeitures vary from the estimate, we recognize the difference in compensation expense in the period the actual forfeitures occur or when options vest.
	All of the aforementioned estimates and assumptions are evaluated on a quarterly basis and may change as facts and circumstances warrant. Changes in these assumptions can materially affect the estimate of the fair value of our share-based payments and the related amount recognized in our financial statements.
	The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options:
		December 31,
		2013		2012		2011
	Volatility		109.20%		117.30%		125.70%
	Risk-free interest rate		1.50%		0.80%		1.50%
	Expected life of option		6.14 years		5.72 years		5.96 years
	Expected dividend yield		0.00%		0.00%		0.00%
	Income Taxes
	Deferred tax liabilities and assets are determined based on the differences between the financial reporting and tax basis of assets and liabilities and are measured using the tax rate and laws currently in effect. We evaluate our deferred income taxes to determine if a valuation allowance should be established against the deferred tax assets or if the valuation allowance should be reduced based on consideration of all available evidence, both positive and negative, using a “more likely than not” standard.
	We had no liability for uncertain income tax positions as of December 31, 2013 and 2012. Our policy is to recognize potential accrued interest and penalties related to the liability for uncertain tax benefits, if applicable, in income tax expense. Net operating loss and credit carryforwards since inception remain open to examination by taxing authorities, and will for a period post utilization.
	Net Loss per Share
	Basic and diluted net loss per share has been computed using the weighted-average number of shares of common stock outstanding during the period. We have outstanding options and warrants that are not used in the calculation of diluted net loss per share because to do so would be anti-dilutive. The following instruments were excluded from the calculation of diluted net loss per share because their effects would be anti-dilutive:
		Year ended December 31,
		2013		2012		2011
	Outstanding options		5,129,579		4,058,184		4,499,601
	Restricted stock units		2,449,346		70,814		39,300
	Outstanding warrants		8,909,027		5,806,853		6,435,496
			16,487,952		9,935,851		10,974,397
	Reclassifications
	Certain prior year amounts have been reclassified to conform with current year presentations.

Equipment

Equipment	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Equipment	'
	C. Equipment
		December 31,
	Equipment consists of (in thousands):	2013			2012
	Laboratory equipment	$	6,703		$	6,741
	Office equipment and leasehold improvements		2,814			3,842
			9,517			10,583
	Accumulated depreciation		(8,184	)		(9,289	)
		$	1,333		$	1,294
	In 2013, we disposed of approximately $1.5 million of obsolete laboratory equipment, office equipment and leasehold improvements, all of which was fully depreciated.

Financial_Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2013
Investments All Other Investments [Abstract]	'
Financial Instruments	'
	D. Financial Instruments
	Fair Value Measurements
	We classify the inputs used to measure fair value into the following hierarchy:
	Level 1	Unadjusted quoted prices in active markets for identical assets or liabilities.
	Level 2	Unadjusted quoted prices in active markets for similar assets or liabilities, or unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability.
	Level 3	Unobservable inputs for the asset or liability.
	The following table provides a summary of the financial assets and liabilities measured at fair value on a recurring basis as follows: (in thousands):
					Fair Value Measurements at December 31, 2013 Using
	Description	Balance as of			Quoted Prices in Active			Significant Other			Significant
		December 31,			Markets for Identical			Observable Inputs			Unobservable
		2013			Assets (Level 1)			(Level 2)			Inputs (Level 3)
	Warrant liabilities	$	9,823		$	—		$	—		$	9,823
					Fair Value Measurements at December 31, 2012 Using
	Description	Balance as of			Quoted Prices in Active			Significant Other			Significant
		December  31,			Markets for Identical			Observable Inputs			Unobservable
		2012			Assets (Level 1)			(Level 2)			Inputs (Level 3)
	Warrant liabilities	$	2,709		$	—		$	—		$	2,709
	We review and reassess the fair value hierarchy classifications on a quarterly basis. Changes from one quarter to the next related to the observability of inputs in a fair value measurement may result in a reclassification between fair value hierarchy levels. There were no reclassifications for all periods presented.
	The estimated fair value of warrants accounted for as liabilities, representing a level 3 fair value measure, was determined on the issuance date and subsequently marked to market at each financial reporting date. The fair value is estimated using the expected volatility based on our historical volatility for warrants issued after January 1, 2013, or for warrants issued prior to 2013, using the historical volatilities of comparable companies from a representative peer group selected based on industry and market capitalization. The fair value of the warrants is determined using probability weighted-average assumptions, when appropriate. The warrants issued in our December 2013 offering were issued in two series, since 1,401,218 of the total 3,500,000 warrants issued are not exercisable until June 3, 2014. The following inputs were used at December 31, 2013:
		“A”			“B”			Warrants Issued			Warrants Issued
		Warrants Issued			Warrants Issued			Mar-12			Feb-11
		Dec-13			Dec-13
	Expected volatility		53.3	%		51.7	%		71.4	%		73.3	%
	Risk-free interest rate		0.13	%		0.13	%		0.78	%		0.38	%
	Expected life		1.25	years		0.82	years		3.20	years		2.09	years
	Fair value at December 31, 2013	$	1,232		$	650		$	6,944		$	997
	(in thousands)
	A roll-forward of fair value measurements using significant unobservable inputs (Level 3) for the warrants is as follows (in thousands):
		Year ended
		December 31, 2013
	Balance January 1, 2013	$	2,709
	Issuance of warrants December 2013		1,186
	Settlements		(396	)
	Loss included in other income (expense), net, for the period		6,324
	Balance December 31, 2013	$	9,823
	Financing Arrangements
	We lease office and laboratory space under operating leases. The lease for our corporate offices and laboratories began in 2000 and currently expires in March 2016, and we have the option to renew annually through 2019. Our rent is $267,000 per year and our rental rate has not changed since the lease inception in 2000. Also, we lease office and laboratory space for our Belgian subsidiary, which currently expires in July 2015 and includes options to renew annually through July 2022, with annual rent of $197,000, subject to adjustments based on an inflationary index
	Aggregate rent expense was approximately $491,000, $415,000 and $397,000 in 2013, 2012 and 2011, respectively. The future annual minimum lease commitments at December 31, 2013 are approximately $483,000 for 2014, $383,000 for 2015, $67,000 for 2016, and $0 for 2017.
	In April 2012, we entered into an arrangement with the Global Cardiovascular Innovation Center and the Cleveland Clinic Foundation pursuant to which we are entitled to proceeds of up to $500,000 in the form of a forgivable loan to fund certain remaining preclinical work using MultiStem to treat congestive heart failure and for preparing the program for an investigational new drug application with the United States Food and Drug Administration. Interest on the loan accrues at a fixed rate of 4.25% per annum, and is added to the outstanding principal. The principal and interest on the loan will be forgiven based on the achievement of a certain milestone, unrelated to the preclinical work, within three to four years. As of December 31, 2013 and 2012, we have drawn $166,000 of this financing, which is reflected on the balance sheet as a non-current note payable, including interest.
	Our former lenders retained a right to receive remaining milestone payments up to $1.3 million as of December 31, 2011 (from an original amount of $2.25 million) upon the occurrence of certain events, and the final balance was settled in full in 2012 in connection with equity offerings during the year. We elected to pay 75% of the milestone payments in shares of common stock at the per-share offering prices in 2012 and $1.3 million in cash and stock-based milestone payments were recognized as other expense in 2012. In 2011, milestone expense was $0.9 million.
	We paid no interest during the three years ended December 31, 2013.

Collaborations_and_Revenue_Rec

Collaborations and Revenue Recognition	12 Months Ended
	Dec. 31, 2013
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Collaborations and Revenue Recognition	'
	E. Collaborations and Revenue Recognition
	Pfizer
	In 2009, we entered into a collaboration with Pfizer Inc. (“Pfizer”) to develop and commercialize our MultiStem® product candidate to treat inflammatory bowel disease (“IBD”) for the worldwide market. Under the terms of the agreement, we received a non-refundable up-front payment from Pfizer and research funding and support through June 2012. In addition, we are eligible to receive milestone payments upon the successful achievement of certain development, regulatory and commercial milestones, for which we evaluated the nature of the events triggering these contingent payments and concluded that these events constituted substantive milestones that will be recognized as revenue in the period in which the underlying triggering event occurs. In concluding that each milestone is substantive, we considered factors such as whether the associated consideration fairly represents either the level of effort required to reach the milestone or the value added to the product based on the achievement of such milestone. No significant milestone revenue has been recognized to date.
	Pfizer pays us for manufacturing product for clinical development and commercialization purposes. Pfizer has responsibility for development, regulatory and commercialization and will pay us tiered royalties on worldwide commercial sales of MultiStem IBD products. Alternatively, in lieu of royalties and certain commercialization milestones, we may elect to co-develop with Pfizer and the parties will share development and commercialization expenses and profits/losses on an agreed basis beginning at Phase 3 clinical development.
	We evaluated the facts and circumstances of the agreement and determined the Pfizer agreement had multiple deliverables that should be combined into a single unit of accounting. We recognized the license and technology access fee and research and development funding ratably on a straight-line basis over the estimated performance period, which was completed mid-2012, and measured manufacturing revenue beginning upon the culmination of the earnings process and recognized it over the performance period of the bundled unit of accounting.
	Angiotech
	In 2011, we reached an agreement with Angiotech to terminate the collaboration agreement and license between the parties, reflecting a change in Angiotech’s business and financial strategy. As a result of the termination, we regained ownership of all rights for developing our stem cell technologies and products for cardiovascular disease indications, including AMI, congestive heart failure, chronic ischemia, and peripheral vascular disease, and Angiotech no longer has any license rights or options with respect to our technologies and products. As part of the termination agreement, if we enter into a new AMI collaboration before November 14, 2014, and at the time of the collaboration, we have made certain progress in development, Angiotech could be eligible for 10% of any third-party license fees up to a maximum of $5.0 million. Angiotech is not entitled to other downstream payments, such as milestone payments, royalties or any profit-sharing payments. Prior to the termination of the collaboration, our clinical costs were recorded net of Angiotech’s cost-share reimbursements, which amounted to $312,000 in 2011.
	RTI Surgical, Inc.
	In 2010, we entered into an agreement with RTI Surgical, Inc. (“RTI”), formerly RTI Biologics, Inc., to develop and commercialize biologic implants using our technology for certain orthopedic applications in the bone graft substitutes market. Under the terms of the agreement, we received a $5.0 million license fee in installments, of which $3.0 million was guaranteed and received in 2010 and 2011, and $2.0 million was contingent upon future events and considered a substantive milestone at the inception of the agreement. We evaluated the facts and circumstances and determined the RTI agreement had obligations constituting deliverables and concluded that it has multiple deliverables, including deliverables relating to the grant of a license to our technology and performance of research and development services, and concluded that these deliverables should be combined into a single unit of accounting. We recognized the $3.0 million guaranteed license fee ratably on a straight-line basis over the estimated performance period, which was completed in 2011.
	In September 2012, RTI agreed to make the remaining $2.0 million license fee payments by December 31, 2012, and we agreed to provide RTI with certain technical support through December 31, 2012. The $2.0 million consideration associated with the amendment was recognized over the performance period from September 2012 through December 2012.
	We are also eligible to receive $35.5 million in cash payments upon the successful achievement of certain commercial milestones. We evaluated the nature of the events triggering these contingent payments and concluded that these events are substantive and that revenue will be recognized in the period in which each underlying triggering event occurs. In addition, we will receive tiered royalties on worldwide commercial sales, if any, of implants using our technologies. No milestone or royalty revenue has been recognized to date.

Capitalization_and_Warrant_Lia

Capitalization and Warrant Liability	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Capitalization and Warrant Liability	'
	F. Capitalization and Warrant Liability
	Capitalization
	At December 31, 2013, we had 150.0 million shares of common stock (100.0 million shares at December 31, 2012) and 10.0 million shares of undesignated preferred stock authorized. No shares of preferred stock have been issued as of December 31, 2013.
	The following shares of common stock were reserved for future issuance:
		December 31
		2013			2012
	Stock-based compensation plans		11,020,510			5,490,181
	Warrants to purchase common stock — former lenders		149,026			149,026
	Warrants to purchase common stock — 2011 offering		1,310,000			1,310,000
	Warrants to purchase common stock — 2012 offering		3,950,001			4,347,827
	Warrants to purchase common stock — 2013 offering		3,500,000			—
			19,929,537			11,297,034
	In January 2014, we completed a registered direct offering generating net proceeds of approximately $18.7 million through the issuance of 5,000,000 shares of common stock and immediately exercisable warrants to purchase 1,500,000 shares of common stock with an exercise price of $4.50 per share that expire on July 15, 2016. The securities were sold in multiples of a fixed combination of one share of common stock and a warrant to purchase 0.30 shares of common stock at an offering price of $4.10 per fixed combination.
	In December 2013, we completed a registered direct offering generating net proceeds of approximately $18.4 million through the issuance of 10,000,000 shares of common stock and warrants to purchase 3,500,000 shares of common stock with an exercise price of $2.50 per share that expire on March 31, 2015. Of the 3,500,000 warrants, 1,401,218 are not exercisable until June 3, 2014. The securities were sold in multiples of a fixed combination of one share of common stock and a warrant to purchase 0.35 shares of common stock at an offering price of $2.00 per fixed combination.
	In October 2012, we completed a public offering generating net proceeds of approximately $18.3 million through the issuance of 19,802,000 shares of common stock at a price of $1.01 per share. In November 2012, the underwriters exercised in full their right to purchase an additional 2,970,300 shares of common stock, solely to cover over-allotments. The exercise of the full over-allotment option generated an additional $2.8 million of net proceeds.
	In March 2012, we completed a private placement financing generating net proceeds of approximately $8.1 million through the issuance of 4,347,827 shares of common stock and five-year warrants to purchase 4,347,827 shares of common stock with an exercise price of $2.07 per share. The securities were sold in multiples of a fixed combination of one share of common stock and a warrant to purchase one share of common stock at an offering price of $2.07 per fixed combination, and the warrants include price protection in the event we sell stock below the exercise price, as defined. As a result of the October 2012 public offering and in accordance with the terms of the warrants, we sought and obtained stockholder approval in February 2013 to reduce the exercise price of these warrants to $1.01 per share.
	In February 2011, we completed a registered direct offering with net proceeds of $11.8 million through the issuance of 4,366,667 shares of common stock and five-year warrants to purchase 1,310,000 shares of common stock with an exercise price of $3.55 per share. The securities were sold in multiples of a fixed combination of one share of common stock and a warrant to purchase 0.3 of a share of common stock at an offering price of $3.00 per fixed combination.
	Aspire Capital
	In November 2011, we entered into an equity purchase agreement, which provides that Aspire Capital Fund, LLC (“Aspire Capital”) is committed to purchase up to an aggregate of $20.0 million of shares of our common stock over a two-year term, subject to our election to sell any such shares. Under the agreement, we have the right to sell shares, subject to certain volume limitations and a minimum floor price, at a modest discount to the prevailing market price. As part of the agreement, Aspire Capital made an initial investment of $1.0 million in us through the purchase of 666,667 shares of our common stock at $1.50 per share in 2011, and received 266,667 additional shares as compensation for its commitment. In 2012, we sold an additional 800,000 shares to Aspire Capital at an average price of $1.57 per share.
	In October 2013, we terminated the expiring 2011 equity purchase agreement with Aspire Capital and entered into a new equity purchase agreement with Aspire Capital to purchase up to an aggregate of $25.0 million of shares of our common stock over a new two-year period. The terms of the 2013 equity facility are similar to the previous arrangement, and we issued 333,333 shares of our common stock Aspire Capital as a commitment fee in October 2013 and filed a registration statement for the resale of 10,000,000 shares of common stock in connection with the new equity facility. In 2013, we sold an aggregate 6,566,666 shares to Aspire Capital at an average price of $1.70 per share under both equity purchase agreements (300,000 shares were sold during the quarter ended December 31, 2013 at an average price of $1.69 per share). As of December 31, 2013, we have received aggregate proceeds of approximately $13.4 million under both equity purchase agreements since their inception.
	Warrant Liabilities
	The warrants we issued in the December 2013 registered direct offering contain a provision for a cash payment in the event that the shares are not delivered to the holder within two trading days. The cash payment equals $10 per day per $2,000 of warrant shares for each day late. The warrants we issued in both the March 2012 private placement and the February 2011 registered direct offering each contain a provision for net cash settlement in the event that there is a fundamental transaction (e.g., merger, sale of substantially all assets, tender offer, or share exchange). If a fundamental transaction occurs in which the consideration issued consists of all cash or stock in a non-public company, then the warrant holder has the option to receive cash equal to a Black Scholes value of the remaining unexercised portion of the warrant. Further, the March 2012 warrants include price protection in the event we sell stock below the exercise price, as defined. As a result of the October 2012 public offering and in accordance with the terms of the warrants, we sought and obtained stockholder approval in February 2013 to reduce the exercise price of these 4,347,827 warrants to $1.01 per share.
	The warrants have been classified as liabilities, as opposed to equity, due to the potential adjustment to the exercise price that could result upon late delivery of the shares or potential cash settlement upon the occurrence of certain events as described above, and are recorded at their fair values at each balance sheet date. See Note D.
	As of December 31, 2013, we had the following outstanding warrants to purchase shares of common stock:
	Number of	Exercise Price		Expiration
	Underlying Shares
	149,026	$5.00		June 8, 2014
	1,310,000	$3.55		February 2, 2016
	3,950,001	$1.01		14-Mar-17
	3,500,000	$2.50		31-Mar-15
	8,909,027

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation	'
	G. Stock-Based Compensation
	We have two incentive plans that authorized an aggregate of 11,500,000 shares of common stock for awards to employees, directors and consultants, which reflects an increase in shares authorized of 6,000,000 that was approved in 2013. These equity incentive plans authorize the issuance of equity-based compensation in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares and units, and other stock-based awards to qualified employees, directors and consultants. As of December 31, 2013, a total of 479,490 shares of common stock have been issued under our equity incentive plans.
	As of December 31, 2013, a total of 3,441,585 shares were available for issuance under our equity compensation plans and stock-based awards to purchase 7,578,925 shares of common stock were outstanding. We recognized $1,523,000, $481,000 and $552,000 of stock-based compensation expense in 2013, 2012 and 2011, respectively.
	Stock Options
	The weighted average fair value of options granted in 2013, 2012 and 2011 was $1.42, $1.21 and $2.30 per share, respectively. The total fair value of options vested during 2013, 2012 and 2011 was $585,000, $420,000 and $570,000, respectively. At December 31, 2013, total unrecognized estimated compensation cost related to unvested stock options was approximately $1,686,000, which is expected to be recognized by mid-2017 using the straight-line method. The weighted average contractual life of unvested options at December 31, 2013 was 9.34 years. The aggregate intrinsic value of fully vested option shares and option shares expected to vest as of December 31, 2013 was $402,000.
	A summary of our stock option activity and related information is as follows:
					Number			Weighted
					of Options			Average
								Exercise
								Price
	Outstanding January 1, 2011					4,308,013		$	4.73
	Granted					213,588			2.61
	Forfeited / Terminated / Expired					(22,000	)		3.46
	Outstanding December 31, 2011					4,499,601			4.63
	Granted					290,150			1.44
	Forfeited / Expired					(731,567	)		4.92
	Outstanding December 31, 2012					4,058,184			4.36
	Granted					1,336,928			1.71
	Exercised					(1,312	)		1.26
	Forfeited / Expired					(264,221	)		3.36
	Outstanding December 31, 2013					5,129,579		$	3.72
	Vested during 2013					383,808		$	1.86
	Vested and exercisable at December 31, 2013					3,896,383		$	4.35
		December 31, 2013
		Options Outstanding								Options Vested and Exercisable
	Exercise Price	Number			Weighted			Weighted		Number		Weighted		Weighted
		of			Average			Average		of		Average		Average
		Options			Remaining			Exercise		Options		Remaining		Exercise
					Contractual			Price				Contractual		Price
					Life							Life
	$1.13 – 2.94		1,988,579			8.18		$	1.86		756,133		6.28	$	2.08
	$3.10 – 5.00		3,033,500			3.37		$	4.88		3,032,750		3.37	$	4.88
	$5.28 – 7.80		107,500			5.98		$	5.28		107,500		5.98	$	5.28
			5,129,579								3,896,383
	Restricted Stock Units
	A summary of our restricted stock unit activity and related information is as follows:
		Number			Weighted
		of			Average
		Restricted			Fair Value
		Stock Units
	Outstanding January 1, 2011		—		$	—
	Granted		39,300			2.69
	Outstanding December 31, 2011		39,300			2.69
	Granted		56,716			1.43
	Vested-common stock issued		(9,819	)		2.69
	Forfeited/expired		(15,383	)		1.88
	Outstanding December 31, 2012		70,814			1.86
	Granted		2,851,964			1.71
	Vested-common stock issued		(468,359	)		1.72
	Forfeited/expired		(5,073	)		1.77
	Outstanding December 31, 2013		2,449,346		$	1.71
	Vested/Issued cumulative at December 31, 2013		478,178		$	1.74
	The weighted average fair value of restricted stock units granted in 2013 was $1.71 per share. The total fair value of restricted stock units vested during 2013, 2012 and 2011 was $805,000, $26,000 and $0, respectively. At December 31, 2013, total unrecognized estimated compensation cost related to unvested restricted stock units was approximately $3,954,000, which is expected to be recognized by mid-2017 using the straight-line method.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	H. Income Taxes
	We had net operating loss and research and development tax credit carryforwards of approximately $26,382,000 and $1,473,000, respectively, at December 31, 2013, and approximately $71,522,000 and $4,176,000, respectively at December 31, 2012. Such losses and credits may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2033 and 2034.
	Additionally, as of December 31, 2013, we have net operating loss carryforwards of approximately $34,521,000 (“Section 382 Limited NOL”) that are limited to an annual net operating loss carryforward of $1,833,000. This limitation under Section 382 of the Internal Revenue Code was a result of our equity offering in October 2012. The Section 382 Limited NOL may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2014 and 2031.
	Significant components of our deferred tax assets are as follows (in thousands):
		December 31,
		2013			2012
	Net operating loss carryforwards	$	8,970		$	24,318
	Net operating loss carryforwards — Section 382 Limited NOL		11,737			2,277
	Research and development credit carryforwards		1,473			4,176
	Compensation expense		3,353			2,948
	Other		509			503
	Total deferred tax assets		26,042			34,222
	Valuation allowance for deferred tax assets		(26,042	)		(34,222	)
	Net deferred tax assets	$	—		$	—
	Because of our cumulative losses, the deferred tax assets have been fully offset by a valuation allowance. We have not paid income taxes for the three-year period ended December 31, 2013.

Profit_Sharing_Plan_and_401k_P

Profit Sharing Plan and 401(k) Plan	12 Months Ended
	Dec. 31, 2013
Postemployment Benefits [Abstract]	'
Profit Sharing Plan and 401(k) Plan	'
	I. Profit Sharing Plan and 401(k) Plan
	We have a profit sharing and 401(k) plan that covers substantially all employees and allows for discretionary contributions by us. We make employer contributions to this plan, and the expense was approximately $97,000 in 2013, $98,000 in 2012, and $88,000 in 2011.

Quarterly_Financial_Data_unaud

Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Data (unaudited)	'
	J. Quarterly Financial Data (unaudited)
	The following table presents quarterly data for the years ended December 31, 2013 and 2012, in thousands, except per share data:
		2013
		First			Second			Third			Fourth			Full Year
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	326		$	571		$	621		$	920		$	2,438
	Net loss	$	(9,388	)	$	(5,946	)	$	(5,614	)	$	(9,795	)	$	(30,743	)
	Basic and diluted net loss per common share	$	(0.18	)	$	(0.11	)	$	(0.10	)	$	(0.15	)	$	(0.53	)
		2012
		First			Second			Third			Fourth			Full Year
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	2,747		$	2,657		$	1,015		$	2,289		$	8,708
	Net loss	$	(4,336	)	$	(3,713	)	$	(3,449	)	$	(3,237	)	$	(14,735	)
	Basic and diluted net loss per common share	$	(0.17	)	$	(0.13	)	$	(0.12	)	$	(0.07	)	$	(0.45	)
	Due to the effect of quarterly changes to outstanding shares of common stock and weightings, the annual loss per share will not necessarily equal the sum of the respective quarters.

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2013
Valuation And Qualifying Accounts [Abstract]	'
Schedule II - Valuation and Qualifying Accounts	'
	The following financial statement schedule of Athersys, Inc. is included:
	Schedule II – Valuation and Qualifying Accounts
	(In thousands)	Balance at		Additions			Deductions			Balance at
		Beginning of								End of Year
		Year
	Year Ended December 31, 2013
	Deducted from asset accounts:
	Allowance for doubtful accounts	$	330	$	—		$	—		$	330
	Tax valuation allowances	$	34,222	$	4,373		$	12,464	(B)	$	26,131
	Total 2013	$	34,552	$	4,373		$	12,464		$	26,461
	Year Ended December 31, 2012
	Deducted from asset accounts:
	Allowance for doubtful accounts	$	307	$	23	(A)	$	—		$	330
	Tax valuation allowances	$	29,272	$	4,950		$	—		$	34,222
	Total 2012	$	29,579	$	4,973		$	—		$	34,552
	Year Ended December 31, 2011
	Deducted from asset accounts:
	Allowance for doubtful accounts	$	296	$	11	(A)	$	—		$	307
	Tax valuation allowances	$	23,908	$	5,364		$	—		$	29.272
	Total 2011	$	24,204	$	5,375		$	—		$	29,579
	(A) –	Reserve on note receivable.
	(B) –	Deferred tax assets are fully offset by valuation allowances. As a result of the October 2012 equity offering and merger, the Company lost the use of a significant portion of its net operating loss carryforwards generated prior to October 2012.

Accounting_Policies_Policies

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Principles of Consolidation	'
	Principles of Consolidation
	The consolidated financial statements include our accounts and results of operations and those of our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Investments in joint ventures are accounted for using the equity method when we do not control the investee, but have the ability to exercise significant influence over the investee’s operations and financial policies. We liquidated our investment in our joint venture in January 2012 and recognized a gain of $183,000.
Revenue Recognition	'
	Revenue Recognition
	Our license and collaboration agreements may contain multiple elements, including license and technology access fees, research and development funding, manufacturing revenue, cost-sharing, milestones and royalties. The deliverables under such an arrangement are evaluated under Accounting Standards Codification (“ASC”) 605-25, Multiple-Element Arrangements. Effective January 1, 2011, we adopted ASU 2009-13, Multiple-Deliverable Revenue Arrangements (“ASU 2009-13”), which amended the guidance in ASC 605-25 on the accounting for arrangements involving the delivery of more than one element. Pursuant to the new standard, each required deliverable is evaluated to determine whether it qualifies as a separate unit of accounting based on whether the deliverable has “stand-alone value” to the customer. The arrangement’s consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. In general, the consideration allocated to each unit of accounting is recognized as the related goods or services are delivered, limited to the consideration that is not contingent upon future deliverables.
	We adopted this new accounting standard on a prospective basis for agreements containing multiple elements entered into on or after January 1, 2011, and for any agreements entered into prior to January 1, 2011, but materially modified on or after that date.
	The primary impact of adopting the new standard is expected to be the earlier recognition of revenue for multiple element arrangements. The adoption of ASU 2009-13 did not affect revenues that we have earned through December 31, 2013. The impact of adopting this new accounting standard is dependent on the terms and conditions of any future arrangements that we may enter into that include multiple elements and arrangements entered into prior to January 1, 2011 that are materially modified. Depending on the terms of any such arrangements, the adoption of this accounting standard may have a material impact on our consolidated results of operations or financial position as it may have the potential effect of less revenue deferral for new collaborations than we have historically experienced.
	For agreements entered into prior to January 1, 2011 and not materially modified thereafter, we continue to apply our prior accounting policy with respect to such arrangements. Under this policy, the deliverables under the arrangement are evaluated to assess whether they have standalone value and objective and reliable evidence of fair value, and if so, are accounted for as a single unit. We then recognize revenue for each unit based on the culmination of the earnings process under ASC 605-S25, issued as Staff Accounting Bulletin (“SAB”) Topic 13, and our estimated performance period for the single units of accounting based on the specific terms of each collaborative agreement. We subsequently adjust the estimated performance periods, if appropriate, on a prospective basis based upon available facts and circumstances. Future changes in estimates of the performance period may materially impact the timing of future revenue recognized. Amounts received prior to satisfying the revenue recognition criteria for contract revenues are recorded as deferred revenue in the accompanying balance sheets. Reimbursement amounts (other than those accounted for using collaboration accounting) paid to us are recorded on a gross basis in the statements of operations as contract revenues.
	We recognize revenue from at-risk, performance milestones that are substantive in the period that the milestone is achieved, as defined in the respective contracts.
	Also included in contract revenue are license fees received from Bristol-Myers Squibb, which are specifically set forth in the license and collaboration agreement as amounts due to us based on our completion of certain tasks (e.g., delivery and acceptance of a cell line) and development milestones (e.g., clinical trial phases), and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced and recorded as revenue as tasks are completed and as milestones are achieved.
	Similarly, grant revenue consists of funding under cost reimbursement programs primarily from federal and state sources for qualified research and development activities performed by us, and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced (unless prepaid) and recorded as revenue as tasks are completed.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	We consider all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents are primarily invested in money market funds and commercial paper. The carrying amount of our cash equivalents approximates fair value due to the short maturity of the investments.
Research and Development	'
	Research and Development
	Research and development expenditures, which consist primarily of costs associated with external clinical and preclinical study fees, manufacturing costs, salaries and related personnel costs, legal expenses resulting from intellectual property application processes, and laboratory supply and reagent costs, including direct and allocated overhead expenses, are charged to expense as incurred.
Collaborative Arrangements	'
	Collaborative Arrangements
	Collaborative arrangements that involve cost or future profit sharing are reviewed to determine the nature of the arrangement and the nature of the collaborative parties’ businesses. The arrangements are also reviewed to determine if one party has sole or primary responsibility for an activity, or whether the parties have shared responsibility for the activity. If responsibility for an activity is shared and there is no principal party, then the related costs of that activity are recognized by us on a net basis in the statement of operations (e.g., total cost less reimbursement from collaborator). If we are deemed to be the principal party for an activity, then the costs and revenues associated with that activity are recognized on a gross basis in the statement of operations. The accounting may be susceptible to change if the nature of a collaborator’s business changes. Our only collaboration accounted for on a net basis was our cost-sharing collaboration with Angiotech Pharmaceuticals, Inc. (“Angiotech”), which was terminated in 2011.
Clinical Trial Costs	'
	Clinical Trial Costs
	Clinical trial costs are accrued based on work performed by outside contractors that manage and perform the trials. We obtain initial estimates of total costs based on enrollment of subjects, project management estimates and other activities. Actual costs are typically charged to us and recognized as the tasks are completed by the contractor, and if we are invoiced based on progress payments as opposed to actual costs, we develop estimates of work completed to date. Accrued clinical trial costs may be subject to revisions as clinical trials progress, and any revisions are recorded in the period in which the facts that give rise to the revisions become known.
Royalties	'
	Royalties
	We may be required to make future royalty payments to certain parties based on product sales under license agreements. We did not pay any royalties during the three-year period ended December 31, 2013.
Investments in Available-for-Sale Securities	'
	Investments in Available-for-Sale Securities
	We determine the appropriate classification of investment securities at the time of purchase and re-evaluate such designation as of each balance sheet date. Our investments typically consist of United States government obligations and corporate debt securities, which are classified as available-for-sale and are valued based on quoted prices in active markets for identical assets (Level 1). Available-for-sale securities are carried at fair value, with the unrealized gains and losses, net of applicable tax, reported as a component of accumulated other comprehensive income. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization or accretion is included in interest income. Realized gains and losses on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific identification method. Interest earned on securities classified as available-for-sale is included in interest income. None of our financial assets are in markets that are not active.
Long-Lived Assets	'
	Long-Lived Assets
	Equipment is stated at acquired cost less accumulated depreciation. Laboratory and office equipment are depreciated on the straight-line basis over the estimated useful lives (three to ten years). Leasehold improvements are amortized over the shorter of the lease term or estimated useful life.
	Long-lived assets are evaluated for impairment when events or changes in circumstances indicate that the carrying amount of the asset or related group of assets may not be recoverable. If the expected future undiscounted cash flows are less than the carrying amount of the asset, an impairment loss is recognized at that time. Measurement of impairment may be based upon appraisal, market value of similar assets or discounted cash flows.
Patent Costs and Rights	'
	Patent Costs and Rights
	Costs of prosecuting and maintaining patents and patent rights are expensed as incurred. As of December 31, 2013, we have filed for broad intellectual property protection on our proprietary technologies. We currently have numerous United States patent applications and corresponding international patent applications related to our technologies, as well as many issued United States and international patents.
Warrant Liabilities	'
	Warrant Liabilities
	We account for common stock warrants as either liabilities or as equity instruments depending on the specific terms of the warrant agreement. Registered common stock warrants that could require cash settlement or liquidated damages are accounted for as liabilities. We classify these warrant liabilities on the consolidated balance sheet as non-current liabilities. The warrant liabilities are revalued at fair value at each balance sheet date subsequent to the initial issuance. We use the Black-Scholes valuation model to value the warrant liabilities at fair value. The fair value is estimated using the expected volatility based on our historical volatility for warrants issued after January 1, 2013, or for warrants issued prior to 2013, using the historical volatilities of comparable companies from a representative peer group selected based on industry and market capitalization. The fair value of the warrants is determined using probability weighted-average assumptions, when appropriate. Changes in the fair market value of the warrant are reflected in the consolidated statement of operations as other income (expense).
Treasury Stock	'
	Treasury Stock
	Treasury stock is recorded at cost and any difference between the cost basis and the selling price of treasury stock is recognized as additional paid-in capital. Treasury stock is relieved on a first-in-first-out basis at actual cost. At December 31, 2013, we had 65,732 shares of common stock held in treasury and available for reissuance.
Comprehensive Income (Loss)	'
	Comprehensive Income (Loss)
	Unrealized gains and losses on our available-for-sale securities, if any, and the proportional share of comprehensive income and loss of our equity method investment, which was liquidated in 2012, are the only components of accumulated other comprehensive income.
Concentration of Credit Risk	'
	Concentration of Credit Risk
	Our accounts receivable are generally comprised of amounts due from collaborators and granting authorities and are subject to concentration of credit risk due to the absence of a large number of customers. At December 31, 2013, the majority of our accounts receivable are due from granting authorities. We do not require collateral from these customers.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Stock-Based Compensation	'
	Stock-Based Compensation
	We recognize stock-based compensation expense on the straight-line method and use a Black-Scholes option-pricing model to estimate the fair value of option awards. The expected term of options granted represent the period of time that option grants are expected to be outstanding. We use the “simplified” method to calculate the expected life of option grants given our limited history of exercise activity and determine volatility by using our historical stock volatility. The fair value of our restricted stock units are equal to the closing price of our common stock on the date of grant and is expensed over the vesting period on a straight-line basis. Estimates of fair value are not intended to predict actual future events or the value ultimately realized by persons that receive equity awards.
	Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. If actual forfeitures vary from the estimate, we recognize the difference in compensation expense in the period the actual forfeitures occur or when options vest.
	All of the aforementioned estimates and assumptions are evaluated on a quarterly basis and may change as facts and circumstances warrant. Changes in these assumptions can materially affect the estimate of the fair value of our share-based payments and the related amount recognized in our financial statements.
	The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options:
		December 31,
		2013		2012		2011
	Volatility		109.20%		117.30%		125.70%
	Risk-free interest rate		1.50%		0.80%		1.50%
	Expected life of option		6.14 years		5.72 years		5.96 years
	Expected dividend yield		0.00%		0.00%		0.00%
Income Taxes	'
	Income Taxes
	Deferred tax liabilities and assets are determined based on the differences between the financial reporting and tax basis of assets and liabilities and are measured using the tax rate and laws currently in effect. We evaluate our deferred income taxes to determine if a valuation allowance should be established against the deferred tax assets or if the valuation allowance should be reduced based on consideration of all available evidence, both positive and negative, using a “more likely than not” standard.
	We had no liability for uncertain income tax positions as of December 31, 2013 and 2012. Our policy is to recognize potential accrued interest and penalties related to the liability for uncertain tax benefits, if applicable, in income tax expense. Net operating loss and credit carryforwards since inception remain open to examination by taxing authorities, and will for a period post utilization.
Net Loss per Share	'
	Net Loss per Share
	Basic and diluted net loss per share has been computed using the weighted-average number of shares of common stock outstanding during the period. We have outstanding options and warrants that are not used in the calculation of diluted net loss per share because to do so would be anti-dilutive. The following instruments were excluded from the calculation of diluted net loss per share because their effects would be anti-dilutive:
		Year ended December 31,
		2013		2012		2011
	Outstanding options		5,129,579		4,058,184		4,499,601
	Restricted stock units		2,449,346		70,814		39,300
	Outstanding warrants		8,909,027		5,806,853		6,435,496
			16,487,952		9,935,851		10,974,397
Reclassifications	'
	Reclassifications
	Certain prior year amounts have been reclassified to conform with current year presentations.

Accounting_Policies_Tables

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Fair Value of Stock-Based Compensation Awards	'
	The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options:
		December 31,
		2013		2012		2011
	Volatility		109.20%		117.30%		125.70%
	Risk-free interest rate		1.50%		0.80%		1.50%
	Expected life of option		6.14 years		5.72 years		5.96 years
	Expected dividend yield		0.00%		0.00%		0.00%
Instruments Excluded from Calculation of Diluted Net Loss Per Share	'
	The following instruments were excluded from the calculation of diluted net loss per share because their effects would be anti-dilutive:
		Year ended December 31,
		2013		2012		2011
	Outstanding options		5,129,579		4,058,184		4,499,601
	Restricted stock units		2,449,346		70,814		39,300
	Outstanding warrants		8,909,027		5,806,853		6,435,496
			16,487,952		9,935,851		10,974,397

Equipment_Tables

Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Equipment	'
		December 31,
	Equipment consists of (in thousands):	2013			2012
	Laboratory equipment	$	6,703		$	6,741
	Office equipment and leasehold improvements		2,814			3,842
			9,517			10,583
	Accumulated depreciation		(8,184	)		(9,289	)
		$	1,333		$	1,294

Financial_Instruments_Tables

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
Investments All Other Investments [Abstract]	'
Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	'
	The following table provides a summary of the financial assets and liabilities measured at fair value on a recurring basis as follows: (in thousands):
					Fair Value Measurements at December 31, 2013 Using
	Description	Balance as of			Quoted Prices in Active			Significant Other			Significant
		December 31,			Markets for Identical			Observable Inputs			Unobservable
		2013			Assets (Level 1)			(Level 2)			Inputs (Level 3)
	Warrant liabilities	$	9,823		$	—		$	—		$	9,823
					Fair Value Measurements at December 31, 2012 Using
	Description	Balance as of			Quoted Prices in Active			Significant Other			Significant
		December  31,			Markets for Identical			Observable Inputs			Unobservable
		2012			Assets (Level 1)			(Level 2)			Inputs (Level 3)
	Warrant liabilities	$	2,709		$	—		$	—		$	2,709
Fair Value of Warrants Based on Historical Volatilities	'
	The following inputs were used at December 31, 2013:
		“A”			“B”			Warrants Issued			Warrants Issued
		Warrants Issued			Warrants Issued			Mar-12			Feb-11
		Dec-13			Dec-13
	Expected volatility		53.3	%		51.7	%		71.4	%		73.3	%
	Risk-free interest rate		0.13	%		0.13	%		0.78	%		0.38	%
	Expected life		1.25	years		0.82	years		3.20	years		2.09	years
	Fair value at December 31, 2013	$	1,232		$	650		$	6,944		$	997
	(in thousands)
Roll-Forward of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) for Warrants	'
	A roll-forward of fair value measurements using significant unobservable inputs (Level 3) for the warrants is as follows (in thousands):
		Year ended
		December 31, 2013
	Balance January 1, 2013	$	2,709
	Issuance of warrants December 2013		1,186
	Settlements		(396	)
	Loss included in other income (expense), net, for the period		6,324
	Balance December 31, 2013	$	9,823

Capitalization_and_Warrant_Lia1

Capitalization and Warrant Liability (Tables)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Common Stock Shares Reserved for Future Issuance	'
	The following shares of common stock were reserved for future issuance:
		December 31
		2013			2012
	Stock-based compensation plans		11,020,510			5,490,181
	Warrants to purchase common stock — former lenders		149,026			149,026
	Warrants to purchase common stock — 2011 offering		1,310,000			1,310,000
	Warrants to purchase common stock — 2012 offering		3,950,001			4,347,827
	Warrants to purchase common stock — 2013 offering		3,500,000			—
			19,929,537			11,297,034
Outstanding Warrants to Purchase Shares of Common Stock	'
	As of December 31, 2013, we had the following outstanding warrants to purchase shares of common stock:
	Number of	Exercise Price		Expiration
	Underlying Shares
	149,026	$5.00		June 8, 2014
	1,310,000	$3.55		February 2, 2016
	3,950,001	$1.01		14-Mar-17
	3,500,000	$2.50		31-Mar-15
	8,909,027

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Summary of Stock Option Activity and Related Information	'
	A summary of our stock option activity and related information is as follows:
					Number			Weighted
					of Options			Average
								Exercise
								Price
	Outstanding January 1, 2011					4,308,013		$	4.73
	Granted					213,588			2.61
	Forfeited / Terminated / Expired					(22,000	)		3.46
	Outstanding December 31, 2011					4,499,601			4.63
	Granted					290,150			1.44
	Forfeited / Expired					(731,567	)		4.92
	Outstanding December 31, 2012					4,058,184			4.36
	Granted					1,336,928			1.71
	Exercised					(1,312	)		1.26
	Forfeited / Expired					(264,221	)		3.36
	Outstanding December 31, 2013					5,129,579		$	3.72
	Vested during 2013					383,808		$	1.86
	Vested and exercisable at December 31, 2013					3,896,383		$	4.35
Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable	'
		December 31, 2013
		Options Outstanding								Options Vested and Exercisable
	Exercise Price	Number			Weighted			Weighted		Number		Weighted		Weighted
		of			Average			Average		of		Average		Average
		Options			Remaining			Exercise		Options		Remaining		Exercise
					Contractual			Price				Contractual		Price
					Life							Life
	$1.13 – 2.94		1,988,579			8.18		$	1.86		756,133		6.28	$	2.08
	$3.10 – 5.00		3,033,500			3.37		$	4.88		3,032,750		3.37	$	4.88
	$5.28 – 7.80		107,500			5.98		$	5.28		107,500		5.98	$	5.28
			5,129,579								3,896,383
Summary of Restricted Stock Unit Activity and Related Information	'
	A summary of our restricted stock unit activity and related information is as follows:
		Number			Weighted
		of			Average
		Restricted			Fair Value
		Stock Units
	Outstanding January 1, 2011		—		$	—
	Granted		39,300			2.69
	Outstanding December 31, 2011		39,300			2.69
	Granted		56,716			1.43
	Vested-common stock issued		(9,819	)		2.69
	Forfeited/expired		(15,383	)		1.88
	Outstanding December 31, 2012		70,814			1.86
	Granted		2,851,964			1.71
	Vested-common stock issued		(468,359	)		1.72
	Forfeited/expired		(5,073	)		1.77
	Outstanding December 31, 2013		2,449,346		$	1.71
	Vested/Issued cumulative at December 31, 2013		478,178		$	1.74

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Components of Deferred Tax Assets	'
	Significant components of our deferred tax assets are as follows (in thousands):
		December 31,
		2013			2012
	Net operating loss carryforwards	$	8,970		$	24,318
	Net operating loss carryforwards — Section 382 Limited NOL		11,737			2,277
	Research and development credit carryforwards		1,473			4,176
	Compensation expense		3,353			2,948
	Other		509			503
	Total deferred tax assets		26,042			34,222
	Valuation allowance for deferred tax assets		(26,042	)		(34,222	)
	Net deferred tax assets	$	—		$	—

Quarterly_Financial_Data_unaud1

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Data	'
	The following table presents quarterly data for the years ended December 31, 2013 and 2012, in thousands, except per share data:
		2013
		First			Second			Third			Fourth			Full Year
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	326		$	571		$	621		$	920		$	2,438
	Net loss	$	(9,388	)	$	(5,946	)	$	(5,614	)	$	(9,795	)	$	(30,743	)
	Basic and diluted net loss per common share	$	(0.18	)	$	(0.11	)	$	(0.10	)	$	(0.15	)	$	(0.53	)
		2012
		First			Second			Third			Fourth			Full Year
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	2,747		$	2,657		$	1,015		$	2,289		$	8,708
	Net loss	$	(4,336	)	$	(3,713	)	$	(3,449	)	$	(3,237	)	$	(14,735	)
	Basic and diluted net loss per common share	$	(0.17	)	$	(0.13	)	$	(0.12	)	$	(0.07	)	$	(0.45	)

Background_Additional_Informat

Background - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
	Segment
Accounting Policies [Abstract]	'
Number of business segments	1

Accounting_Policies_Additional

Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Jan. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Significant Accounting Policies [Line Items]	'	'	'
Recognized gain on investment in joint venture	$183,000	'	'
Liquid investments with a maturity	'	'Three months or less	'
Payments for Royalties	'	0	'
Common stock shares held in treasury	'	65,732	'
Liability for uncertain income tax	'	$0	$0
Minimum [Member]	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Estimated useful life of long-lived assets	'	'3 years	'
Maximum [Member]	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Estimated useful life of long-lived assets	'	'10 years	'

Accounting_Policies_Fair_Value

Accounting Policies - Fair Value of Stock-Based Compensation Awards (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]	'	'	'
Volatility	109.20%	117.30%	125.70%
Risk-free interest rate	1.50%	0.80%	1.50%
Expected life of option	'6 years 1 month 21 days	'5 years 8 months 19 days	'5 years 11 months 16 days
Expected dividend yield	0.00%	0.00%	0.00%

Accounting_Policies_Instrument

Accounting Policies - Instruments Excluded from Calculation of Diluted Net Loss Per Share (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Total	16,487,952	9,935,851	10,974,397
Outstanding options [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Total	5,129,579	4,058,184	4,499,601
Restricted stock units [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Total	2,449,346	70,814	39,300
Outstanding warrants [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Total	8,909,027	5,806,853	6,435,496

Equipment_Equipment_Detail

Equipment - Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Equipment, Gross	$9,517	$10,583
Accumulated depreciation	-8,184	-9,289
Equipment, net	1,333	1,294
Laboratory equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Equipment, Gross	6,703	6,741
Office equipment and leasehold improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Equipment, Gross	$2,814	$3,842

Equipment_Additional_Informati

Equipment - Additional Information (Detail) (Office and Laboratory Equipment and Leasehold Improvements [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013
Office and Laboratory Equipment and Leasehold Improvements [Member]	'
Property, Plant and Equipment [Line Items]	'
Disposal of obsolete equipment	$1.50

Financial_Instruments_Summary_

Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (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]	'	'
Warrant liabilities	$9,823	$2,709
Fair Value Measurements, Recurring Basis [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Warrant liabilities	9,823	2,709
Fair Value Measurements, Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Warrant liabilities	'	'
Fair Value Measurements, Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Warrant liabilities	'	'
Fair Value Measurements, Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Warrant liabilities	$9,823	$2,709

Financial_Instruments_Addition

Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended			36 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Apr. 30, 2012	Mar. 31, 2012	Feb. 28, 2011
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'	'	'	'
Common stock purchased under warrants	3,500,000	'	'	3,500,000	'	4,347,827	1,310,000
Number of warrants not exercisable	1,401,218	'	'	'	'	'	'
Rent	$267,000	'	'	'	'	'	'
Lease expiration period	'2016-03	'	'	'	'	'	'
Aggregate rent expense	491,000	415,000	397,000	'	'	'	'
Future annual minimum lease commitments for 2014	483,000	'	'	483,000	'	'	'
Future annual minimum lease commitments for 2015	383,000	'	'	383,000	'	'	'
Future annual minimum lease commitments for 2016	67,000	'	'	67,000	'	'	'
Future annual minimum lease commitments for 2017	0	'	'	0	'	'	'
Forgivable loan	'	'	'	'	500,000	'	'
Interest on forgivable loan	'	'	'	'	4.25%	'	'
Non current note payable	176,000	169,000	'	176,000	'	'	'
Period for loan forgivable	'three to four years	'	'	'	'	'	'
Right to receive remaining milestone payments	'	'	1,300,000	'	'	'	'
Original amount	'	'	2,250,000	'	'	'	'
Milestone in share of common stock	'	75.00%	'	'	'	'	'
Milestone payments were paid to the lenders	'	1,300,000	900,000	'	'	'	'
Interest paid	'	'	'	0	'	'	'
Belgium [Member]	'	'	'	'	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'	'	'	'	'
Rent	$197,000	'	'	'	'	'	'
Lease expiration period	'2015-07	'	'	'	'	'	'

Financial_Instruments_Fair_Val

Financial Instruments - Fair Value of Warrants Based on Historical Volatilities (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
"A" Warrants Issued December 2013 [Member]	'
Class of Warrant or Right [Line Items]	'
Expected volatility	53.30%
Risk-free interest rate	0.13%
Expected life (in years)	'1 year 3 months
Fair value at December 31, 2013	$1,232
"B" Warrants Issued December 2013 [Member]	'
Class of Warrant or Right [Line Items]	'
Expected volatility	51.70%
Risk-free interest rate	0.13%
Expected life (in years)	'9 months 26 days
Fair value at December 31, 2013	650
Warrants Issued March 2012 [Member]	'
Class of Warrant or Right [Line Items]	'
Expected volatility	71.40%
Risk-free interest rate	0.78%
Expected life (in years)	'3 years 2 months 12 days
Fair value at December 31, 2013	6,944
Warrants Issued February 2011 [Member]	'
Class of Warrant or Right [Line Items]	'
Expected volatility	73.30%
Risk-free interest rate	0.38%
Expected life (in years)	'2 years 1 month 2 days
Fair value at December 31, 2013	$997

Financial_Instruments_RollForw

Financial Instruments - Roll-Forward of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) for Warrants (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'
Loss included in other income (expense), net, for the period	($6,324)	$2,404	$812
Outstanding warrants [Member]	'	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'	'
Beginning Balance	2,709	'	'
Issuance of warrants December 2013	1,186	'	'
Settlements	-396	'	'
Loss included in other income (expense), net, for the period	6,324	'	'
Ending Balance	$9,823	'	'

Collaborations_and_Revenue_Rec1

Collaborations and Revenue Recognition - Additional Information (Detail) (USD $)	4 Months Ended	12 Months Ended						24 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
			Pfizer [Member]	Angiotech [Member]	Angiotech [Member]	Rti Surgical Inc [Member]	Rti Surgical Inc [Member]	Rti Surgical Inc [Member]
Collaborative Arrangements And Revenue Recognition [Line Items]	'	'	'	'	'	'	'	'
Commercial milestone revenue	'	'	$0	'	'	$0	$0	'
Percentage of third party license fees	'	'	'	10.00%	'	'	'	'
Maximum license fees paid	'	'	'	5,000,000	'	'	'	'
Clinical costs were recorded net of cost-share reimbursements	'	'	'	'	312,000	'	'	'
License fee recognized	2,000,000	'	'	'	'	5,000,000	'	3,000,000
Contingent license fee payments	'	'	'	'	'	2,000,000	'	'
Additional cash payment receivable contingent	'	35,500,000	'	'	'	'	'	'
Royalty revenue	'	'	'	'	'	$0	$0	'

Capitalization_and_Warrant_Lia2

Capitalization and Warrant Liability - Additional Information (Detail) (USD $)

1 Months Ended

12 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

1 Months Ended

Dec. 31, 2013

Nov. 30, 2012

Oct. 31, 2012

Mar. 31, 2012

Feb. 28, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Feb. 28, 2013

Jan. 31, 2014

Nov. 30, 2012

Oct. 31, 2013

Nov. 30, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Nov. 30, 2011

Scenario, Forecast [Member]

Underwriters [Member]

Aspire [Member]

Aspire [Member]

Aspire [Member]

Aspire [Member]

Aspire [Member]

Aspire [Member]

Aspire [Member]

Equity Purchase Agreement [Member]

Class of Warrant or Right [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares authorized

150,000,000

'

'

'

'

150,000,000

100,000,000

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares authorized

10,000,000

'

'

'

'

10,000,000

10,000,000

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares issued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net proceeds through issuance of common stock

$18,400,000

$2,800,000

$18,300,000

$8,100,000

$11,800,000

$29,454,000

$30,357,000

$12,595,000

'

$18,700,000

'

'

'

'

'

$13,400,000

'

'

Issuance of common stock, new issues

'

'

19,802,000

4,347,827

4,366,667

10,000,000

'

'

'

5,000,000

2,970,300

'

666,667

300,000

0

6,566,666

800,000

'

Common stock exercise price

2.5

'

'

2.07

3.55

2.5

'

'

1.01

4.5

'

'

'

'

'

'

'

'

Common stock purchased under warrants

3,500,000

'

'

4,347,827

1,310,000

3,500,000

'

'

'

1,500,000

'

'

'

'

'

'

'

'

Common stock at an offering price of fixed combination

'

'

'

$2.07

$3

$2

'

'

'

$4.10

'

'

'

'

'

'

'

'

Ratio of common stock to warrant in fixed combination

'

'

'

'

0.30%

0.35%

'

'

'

0.30%

'

'

'

'

'

'

'

'

Shares of common stock and warrants expiration date

31-Mar-15

'

'

'

'

31-Mar-15

'

'

'

15-Jul-16

'

'

'

'

'

'

'

'

Warrants exercisable beginning date

'

'

'

'

'

3-Jun-14

'

'

'

'

'

'

'

'

'

'

'

'

Number of warrants not exercisable until June 3, 2014

'

'

'

'

'

1,401,218

'

'

'

'

'

'

'

'

'

'

'

'

Issuance of common stock shares per share

'

'

$1.01

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock warrants period

'

'

'

'5 years

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity purchase agreement, value

'

'

'

'

'

'

'

'

'

'

'

25,000,000

20,000,000

'

'

'

'

'

Equity purchase agreement, term

'

'

'

'

'

'

'

'

'

'

'

'2 years

'2 years

'

'

'

'

'

Initial investment

'

'

'

'

'

'

'

'

'

'

'

'

$1,000,000

'

'

'

'

'

Common stock per share

'

'

'

'

'

'

'

'

'

'

'

'

$1.50

'

'

'

'

'

Common stock issuance (shares) under equity purchase agreement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

266,667

Sale of additional shares at an average price

'

'

'

'

'

'

'

'

'

'

'

'

'

$1.69

'

$1.70

$1.57

'

Common stock issued as commitment fees

'

'

'

'

'

'

'

'

'

'

'

333,333

'

'

'

'

'

'

Common stock registered for resale

'

'

'

'

'

'

'

'

'

'

'

10,000,000

'

'

'

'

'

'

Terms of issuance of warrant demanding cash payments

'

'

'

'

'

'The warrants issued in December 2013 registered direct offering contain a provision for a cash payment in the event that the shares are not delivered to the holder within two trading days. The cash payment equals $10 per day per $2,000 of warrant shares for each day late.

'

'

'

'

'

'

'

'

'

'

'

'

Capitalization_and_Warrant_Lia3

Capitalization and Warrant Liability - Common Stock Shares Reserved for Future Issuance (Detail)	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common Stock Shares Reserved For Future Issuance	19,929,537	11,297,034
Stock-based compensation plans [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common Stock Shares Reserved For Future Issuance	11,020,510	5,490,181
Warrants to purchase common stock former lenders [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common Stock Shares Reserved For Future Issuance	149,026	149,026
Warrants to purchase common stock 2011 offering [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common Stock Shares Reserved For Future Issuance	1,310,000	1,310,000
Warrants to purchase common stock 2012 offering [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common Stock Shares Reserved For Future Issuance	3,950,001	4,347,827
Warrants to purchase common stock - 2013 offering [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Common Stock Shares Reserved For Future Issuance	3,500,000	'

Capitalization_and_Warrant_Lia4

Capitalization and Warrant Liability - Outstanding Warrants to Purchase Shares of Common Stock (Detail)	Dec. 31, 2013	Feb. 28, 2013	Mar. 31, 2012	Feb. 28, 2011
Class of Warrant or Right [Line Items]	'	'	'	'
Number of Underlying Shares	8,909,027	'	'	'
Exercise Price	2.5	1.01	2.07	3.55
June 8, 2014 [Member]	'	'	'	'
Class of Warrant or Right [Line Items]	'	'	'	'
Number of Underlying Shares	149,026	'	'	'
Exercise Price	5	'	'	'
Expiration	8-Jun-14	'	'	'
February 2, 2016 [Member]	'	'	'	'
Class of Warrant or Right [Line Items]	'	'	'	'
Number of Underlying Shares	1,310,000	'	'	'
Exercise Price	3.55	'	'	'
Expiration	2-Feb-16	'	'	'
March 14, 2017 [Member]	'	'	'	'
Class of Warrant or Right [Line Items]	'	'	'	'
Number of Underlying Shares	3,950,001	'	'	'
Exercise Price	1.01	'	'	'
Expiration	14-Mar-17	'	'	'
March 31, 2015 [Member]	'	'	'	'
Class of Warrant or Right [Line Items]	'	'	'	'
Number of Underlying Shares	3,500,000	'	'	'
Exercise Price	2.5	'	'	'
Expiration	31-Mar-15	'	'	'

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Number of incentive plans	2	'	'
Common stock authorized for equity incentive plans	11,500,000	'	'
Common stock shares issued	479,490	'	'
Increase in share authorized	6,000,000	'	'
Shares available for issuance	19,929,537	11,297,034	'
Shares of common stock outstanding	7,578,925	'	'
Stock-based compensation expense	$1,523,000	$481,000	$552,000
Weighted average fair value of options granted	$1.42	$1.21	$2.30
Total fair value of options vested	585,000	420,000	570,000
Total unrecognized estimated compensation cost	1,686,000	'	'
Weighted average contractual life of unvested options	'9 years 4 months 2 days	'	'
Intrinsic value of fully vested option shares	402,000	'	'
Compensation cost related to unvested stock-based awards not yet recognized, expected year for recognition	'2017	'	'
Weighted average fair value, granted	$1.71	'	'
Restricted stock vested	805,000	26,000	0
Estimated compensation cost of unvested restricted stock	$3,954,000	'	'
Equity compensation plans & stock-based awards [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Shares available for issuance	3,441,585	'	'

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary Of Stock Option Activities [Line Items]	'	'	'
Weighted Average Exercise Price Outstanding, Beginning Balance	$4.36	$4.63	$4.73
Weighted Average Exercise Price, Granted	$1.71	$1.44	$2.61
Weighted Average Exercise Price, Exercised	$1.26	'	'
Weighted Average Exercise Price, Forfeited/Terminated/ Expired	$3.36	$4.92	$3.46
Weighted Average Exercise Price Outstanding, Ending Balance	$3.72	$4.36	$4.63
Weighted Average Exercise Price, Vested during 2013	$1.86	'	'
Weighted Average Exercise Price, Vested and exercisable at December 31, 2013	$4.35	'	'
Outstanding options [Member]	'	'	'
Summary Of Stock Option Activities [Line Items]	'	'	'
Number of Options Outstanding, Beginning Balance	4,058,184	4,499,601	4,308,013
Number of Options, Granted	1,336,928	290,150	213,588
Number of Options, Exercised	-1,312	'	'
Number of Options, Forfeited/Terminated/ Expired	-264,221	-731,567	-22,000
Number of Options Outstanding, Ending Balance	5,129,579	4,058,184	4,499,601
Number of Options, Vested during 2013	383,808	'	'
Number of Options, Vested and exercisable at December 31, 2013	3,896,383	'	'

StockBased_Compensation_Summar1

Stock-Based Compensation - Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Options outstanding, Number of Options	5,129,579
Options Vested and Exercisable, Number of Options	3,896,383
1.13 - 2.94 Exercise Price [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Exercise price lower range	$1.13
Exercise price upper range	$2.94
Options outstanding, Number of Options	1,988,579
Option Outstanding, Weighted Average Remaining Contractual Life	'8 years 2 months 5 days
Options Outstanding, Weighted Average Exercise Price	$1.86
Options Vested and Exercisable, Number of Options	756,133
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	'6 years 3 months 11 days
Options Vested and Exercisable, Weighted Average Exercise Price	$2.08
3.10 - 5.00 Exercise Price [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Exercise price lower range	$3.10
Exercise price upper range	$5
Options outstanding, Number of Options	3,033,500
Option Outstanding, Weighted Average Remaining Contractual Life	'3 years 4 months 13 days
Options Outstanding, Weighted Average Exercise Price	$4.88
Options Vested and Exercisable, Number of Options	3,032,750
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	'3 years 4 months 13 days
Options Vested and Exercisable, Weighted Average Exercise Price	$4.88
5.28 -7.80 Exercise Price [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Exercise price lower range	$5.28
Exercise price upper range	$7.80
Options outstanding, Number of Options	107,500
Option Outstanding, Weighted Average Remaining Contractual Life	'5 years 11 months 23 days
Options Outstanding, Weighted Average Exercise Price	$5.28
Options Vested and Exercisable, Number of Options	107,500
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	'5 years 11 months 23 days
Options Vested and Exercisable, Weighted Average Exercise Price	$5.28

StockBased_Compensation_Summar2

Stock-Based Compensation - Summary of Restricted Stock Unit Activity and Related Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Number of Restricted Stock Units, Vested/issued	-805,000	-26,000	0
Weighted average fair value, granted	$1.71	'	'
Restricted Stock Units (RSUs) [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Number of Restricted Stock Units, Outstanding, Beginning balance	70,814	39,300	'
Number of Restricted Stock Units, Granted	2,851,964	56,716	39,300
Number of Restricted Stock Units, Vested/issued	-468,359	-9,819	'
Number of Restricted Stock Units, Forfeited / Expired	-5,073	-15,383	'
Number of Restricted Stock Units, Outstanding, Ending balance	2,449,346	70,814	39,300
Number of Restricted Stock Units, Vested/Issued Cumulative	478,178	'	'
Weighted Average Fair Value, Beginning Balance	$1.86	2.69	'
Weighted average fair value, granted	$1.71	1.43	2.69
Weighted Average Fair Value, Vested/Issued	$1.72	2.69	'
Weighted Average Fair Value, Forfeited/Expired	$1.77	1.88	'
Weighted Average Fair Value, Ending Balance	$1.71	1.86	2.69
Weighted Average Fair Value Vested and Exercisable	$1.74	'	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]	'	'
Net operating loss	$26,382,000	$71,522,000
Research and development tax credit	1,473,000	4,176,000
Operating loss carryforwards, expiration dates	'Expire at various dates between 2033 and 2034.	'
Net operating loss carry forward	34,521,000	'
Annual net operating loss	1,833,000	'
Income tax paid	$0	'
Pre-Merger NOL [Member]	'	'
Income Taxes [Line Items]	'	'
Operating loss carryforwards, expiration dates	'Expire at various dates between 2014 and 2031.	'

Income_Taxes_Components_of_Def

Income Taxes - Components of Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]	'	'
Net operating loss carryforwards	$8,970,000	$24,318,000
Net operating loss carryforwards - Section 382 Limited NOL	11,737,000	2,277,000
Research and development credit carryforwards	1,473,000	4,176,000
Compensation expense	3,353,000	2,948,000
Other	509,000	503,000
Total deferred tax assets	26,042,000	34,222,000
Valuation allowance for deferred tax assets	-26,042,000	-34,222,000
Net deferred tax assets	'	'

Profit_Sharing_Plan_and_401_k_

Profit Sharing Plan and 401 (k) Plan - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Postemployment Benefits [Abstract]	'	'	'
Employer contribution for profit sharing plan	$97,000	$98,000	$88,000

Quarterly_Financial_Data_Quart

Quarterly Financial Data - 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
Net Income Loss Available To Common Stockholders Basic [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Revenues	$920	$621	$571	$326	$2,289	$1,015	$2,657	$2,747	$2,438	$8,708	$10,344
Net loss	($9,795)	($5,614)	($5,946)	($9,388)	($3,237)	($3,449)	($3,713)	($4,336)	($30,743)	($14,735)	($13,746)
Basic and diluted net loss per common share	($0.15)	($0.10)	($0.11)	($0.18)	($0.07)	($0.12)	($0.13)	($0.17)	($0.53)	($0.45)	($0.59)

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at Beginning of Year	$34,552	$29,579	$24,204
Additions	4,373	4,973	5,375
Deductions	12,464	'	'
Balance at End of Year	26,461	34,552	29,579
Allowance for Doubtful Accounts [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at Beginning of Year	330	307	296
Additions	'	23	11
Deductions	'	'	'
Balance at End of Year	330	330	307
Tax valuation allowances [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Balance at Beginning of Year	34,222	29,272	23,908
Additions	4,373	4,950	5,364
Deductions	12,464	'	'
Balance at End of Year	$26,131	$34,222	$29,272