Cellular Dynamics International (ICEL) 10-K 5 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Mar. 02, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	CELLULAR DYNAMICS INTERNATIONAL, INC.
Entity Central Index Key	1482080
Current Fiscal Year End Date	-19
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		15,814,008
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$197,400

Balance_Sheets

Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$34,408	$62,029
Accounts receivable	4,291	3,318
Inventories	4,456	3,884
Prepaid expenses and other assets	1,046	964
Total current assets	44,201	70,195
Property and equipment, net	3,832	2,052
Goodwill	6,817	6,817
Intangible assets, net	3,813	4,122
Debt issuance costs, net	150	199
Other assets	17	10
Total	58,830	83,395
Current liabilities:
Accounts payable	1,815	1,811
Accrued liabilities	3,150	3,361
Deferred revenue	3,918	1,439
Current maturities of long-term debt	4,541	18
Total current liabilities	13,424	6,629
Long-term debt, less current portion	7,590	11,879
Commitments and contingencies (Note 10)
Shareholders' equity:
Convertible preferred stock	0	0
Common stock, $0.0001 par value — authorized, 100,000,000 shares at December 31, 2013 and December 31, 2014; issued and outstanding, 15,757,725 shares at December 31, 2013 and 15,814,008 at December 31, 2014	2	2
Additional paid-in capital	175,433	171,907
Accumulated deficit	137,619	107,022
Total shareholders' equity	37,816	64,887
Total	$58,830	$83,395

Balance_Sheets_Parenthetical

Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Preferred Stock Par Value (in dollars per share)	$0.01	$0.01
Authorized Preferred Stock (in shares)	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock Outstanding (in shares)	0	0
Common Stock Par Value (in dollars per share)	$0.00	$0.00
Common Stock Authorized (in shares)	100,000,000	100,000,000
Common Stock Issued (in shares)	15,814,008	15,757,725
Common Stock Outstanding (in shares)	15,814,008	15,757,725

Statement_of_Operations

Statement of Operations (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Product sales	$8,077	$7,998	$5,178
Collaborations, partnerships and other revenues	8,615	3,886	1,404
Total revenues	16,692	11,884	6,582
Costs and expenses:
Cost of product sales	2,436	2,302	2,089
Research and development	22,435	16,622	14,301
Sales and marketing	8,324	6,516	4,398
General and administrative	12,750	10,707	8,024
Total costs and expenses	45,945	36,147	28,812
Loss from operations	-29,253	-24,263	-22,230
Other (expense) income:
Interest expense	-1,345	-716	-34
Other income	1	21	0
Total other expense	-1,344	-695	-34
Net loss	($30,597)	($24,958)	($22,264)
Net loss per share of common stock, basic and diluted	($1.94)	($3.17)	($12.89)
Weighted average number of shares used in computing net loss per share of common stock, basic and diluted	15,774,814	7,878,060	1,727,086

Shareholders_Equity_Statement

Shareholders' Equity Statement (USD $)	Total	Preferred Series A [Member]	Preferred Series B [Member]	Common [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
In Thousands, except Share data, unless otherwise specified
Beginning Balance at Dec. 31, 2011	$47,022	$28,191	$70,428	$0	$8,203	($59,800)
Beginning Balance (in shares) at Dec. 31, 2011		2,914,187	5,572,000	1,713,355
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Stock (in shares)			1,660,092
Issuance of stock	20,985		20,985
Exercise of stock options (in shares)	20,296			20,296
Exercise of stock options	151				151
Stock-based compensation	1,097				1,097
Net loss	-22,264					-22,264
Ending Balance at Dec. 31, 2012	46,991	28,191	91,413	0	9,451	-82,064
Ending Balance (in shares) at Dec. 31, 2012		2,914,187	7,232,092	1,733,651
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Stock (in shares)				3,846,000
Issuance of stock	40,772			1	40,771
Conversion of Preferred Stock (in shares)		-2,914,187	-7,232,092	10,146,279
Conversion of Preferred Stock	0	-28,191	-91,413	1	119,603
Issuance of stock options for intangible assets	70				70
Warrants issued with long-term debt	241				241
Exercise of warrants (in shares)				8,208
Exercise of warrants	1				1
Exercise of stock options (in shares)	23,587			23,587
Exercise of stock options	155				155
Stock-based compensation	1,615				1,615
Net loss	-24,958					-24,958
Ending Balance at Dec. 31, 2013	64,887	0	0	2	171,907	-107,022
Ending Balance (in shares) at Dec. 31, 2013		0	0	15,757,725
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock options for intangible assets	120				120
Exercise of stock options (in shares)	56,283			56,283
Exercise of stock options	345				345
Stock-based compensation	3,061				3,061
Net loss	-30,597					-30,597
Ending Balance at Dec. 31, 2014	$37,816	$0	$0	$2	$175,433	($137,619)
Ending Balance (in shares) at Dec. 31, 2014		0	0	15,814,008

Statement_of_Cash_Flows

Statement of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	($30,597)	($24,958)	($22,264)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,103	800	1,086
Amortization of licenses, patents and other agreements	584	522	347
Amortization of debt issuance costs and debt discount	107	50	0
Stock-based compensation	3,061	1,615	1,097
Other	-1	-20	6
Changes in operating assets and liabilities:
Accounts receivable	-973	-660	-1,735
Inventories	-572	-1,503	344
Prepaid expenses and other current assets	-89	-302	-322
Accounts payable	41	614	-87
Accrued liabilities	-250	1,558	288
Accrued interest	194	115	0
Deferred revenue	2,479	869	236
Net cash used in operating activities	-24,913	-21,300	-21,004
Cash flows from investing activities:
Purchases of property and equipment	-2,907	-1,817	-132
Proceeds from Sale of Property, Plant, and Equipment	12	0	0
Payments to acquire licenses	-140	-404	-2,395
Net cash used in investing activities	-3,035	-2,221	-2,527
Cash flows from financing activities:
Repayments of debt	-18	-1,055	-434
Proceeds from debt	0	12,000	0
Payments of debt issuance costs	0	-222	0
Proceeds from exercise of stock options	345	155	151
Proceeds from issuance of preferred stock	0	0	20,985
Proceeds from issuance of common stock, net of offering costs	0	40,772	0
Net cash provided by financing activities	327	51,650	20,702
Net increase (decrease) in cash and cash equivalents	-27,621	28,129	-2,829
Cash and cash equivalents — Beginning of period	62,029	33,900	36,729
Cash and cash equivalents — End of period	34,408	62,029	33,900
Supplemental disclosure of cash flow information —
Cash paid for interest	949	545	36
Supplemental information on noncash activities:
Issuance of stock options for intangible assets	120	70	0
Warrants issued with long-term debt	0	261	0
Property and equipment not yet paid	149	162	0
Licenses not yet paid	15	25	0
Accrued interest converted to principal	$0	$0	$66

Description_of_business

Description of business	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of business
	1	Description of business
	Cellular Dynamics International, Inc. (the Company), was incorporated in Wisconsin in late 2007 under the name iPS Cells, Inc. (iPS). In July 2008, the Company acquired two companies—Cellular Dynamics International, Inc. (CDI) and Stem Cell Products, Inc. (SCP)—in a common stock merger transaction. Subsequent to the acquisitions, the combined entity was renamed Cellular Dynamics International, Inc.
	The Company develops and produces fully functioning human cells in industrial quantities to precise specifications. Its proprietary products include true human cells in multiple cell types (iCell products), human induced pluripotent stem cells (iPSCs) and custom iPSCs and iCell products (MyCell products). Its products provide standardized, easy-to-use, cost-effective access to the human cell, the smallest fully functioning operating unit of human biology. Customers use the Company's products, among other purposes, for drug discovery and screening; to test the safety and efficacy of their small molecule and biologic drug candidates; for stem cell banking; and in the research and development of cellular therapeutics.
	On June 27, 2013, the Company’s Board of Directors authorized a 1 for 9.75 reverse split of its Series A preferred stock, Series B preferred stock and common stock which was effective July 9, 2013. These financial statements give retroactive effect to the stock split.

Basis_of_presentation_and_use_

Basis of presentation and use of estimates (Notes)	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	2.    Basis of presentation and use of estimates
	Basis of presentation and use of estimates – The accompanying financial statements have been presented in conformity with accounting principles generally accepted in the United States of America (GAAP). The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions include primarily those required in the valuation of inventory, patents, licenses, goodwill, intangible assets, and property and equipment; the timing of revenue recognition; and the calculation of stock-based compensation. Management bases its estimates on certain assumptions, which it believes are reasonable in the circumstances, and while actual results could differ from those estimates, management does not believe that any change in those assumptions in the near term would have a significant effect on the Company’s financial position, results of operations or cash flows.

Significant_accounting_policie

Significant accounting policies and supplemental financial information	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Significant accounting policies and supplemental financial information	3.    Significant accounting policies and supplemental financial information
	Cash and cash equivalents – The Company considers all highly liquid, short-term investments with original maturities of three months or less to be cash and cash equivalents.
	Accounts receivable – The Company establishes an allowance for doubtful accounts based on a customer's ability and likelihood to pay. There was no allowance at either December 31, 2013 or December 31, 2014.
	The Company does not accrue interest on past due amounts. Past due accounts are determined based on customer terms, the policy for write-offs and collection efforts is based upon individual account circumstances.
	Inventories – Inventories are valued at the lower of cost or market using the weighted-average cost method. The weighted-average method examines total production volume and total labor and overhead over an appropriate historical period and establishes a weighted-average value of materials, overhead and labor to be assigned to each unit of finished goods inventory.
	Inventory includes finished goods that may be used by the Company’s research and development, technical services and marketing groups. When such products are consumed internally they are expensed at their inventoried cost to the appropriate department.
	Provisions, when required, for slow moving, excess and obsolete inventories are recorded to reduce inventory values from cost to their estimated net realizable values, based on product life cycle, development plans, product expiration and quality issues.
	Inventories at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Raw materials	$	1,658		$	1,598
	Work in process	547			436
	Finished goods	1,679			2,422
	Total	$	3,884		$	4,456
	Prepaid expenses and other current assets – Prepaid expenses and other current assets consist of insurance premiums, annual maintenance contracts and other miscellaneous payments and deposits.
	Property and equipment – Property and equipment are recorded at cost and are depreciated using the straight-line method over the useful life of the assets, which is three to seven years. Leasehold improvements are depreciated over the shorter of their estimated useful life or the lease term.
	Property and equipment at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Leasehold improvements	$	451		$	835
	Production and lab equipment	4,815			7,274
	Office and computer equipment	546			1,354
	Construction-in-progress	932			162
		6,744			9,625
	Less accumulated depreciation and amortization	(4,692		)	(5,793		)
	Total	$	2,052		$	3,832
	Impairment of long-lived assets – The Company reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be fully recoverable. An impairment loss would be recognized when the estimated future cash flows from the use of the asset are less than the carrying amount of that asset. No impairment losses were recorded in either 2013 or 2014.
	Goodwill – The entire balance of goodwill resulted from the 2008 acquisition of two companies and represents the purchase price in excess of identifiable assets and in-process research and development acquired in that transaction. Goodwill is not amortized.  The Company has a single reporting unit and all goodwill relates to that unit.
	Goodwill, which has an indefinite useful life, represents the excess of cost over fair value of net assets acquired. Goodwill is reviewed for impairment at least annually during the fourth quarter, or more frequently if an event occurs indicating the potential for impairment. The Company conducts an assessment of qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the Company determines that it is more likely than not that the fair value of its reporting unit is less than its carrying amount, it then conducts a two-part test for impairment of goodwill. The qualitative factors which the Company may assess during the qualitative approach include, but are not limited to, macroeconomic conditions, industry and market considerations, the overall financial performance of the Company, and the excess of prior year estimates of fair value compared to carrying value. Based on this qualitative assessment, management concluded that as of the 2014 annual impairment test date, it was more likely than not that the fair value of the reporting unit was greater than its carrying value, and no further testing was performed.
	The Company performed its annual assessment for goodwill impairment in the fourth quarters of 2013 and 2014, noting no impairment in either year. The Company has not recorded any impairment of goodwill since the amount was recorded in 2008.
	Intangible assets – Intangible assets consist of licenses, patents, trade name and a noncompetition agreement with a scientific founder.
	The Company expenses patent related costs as incurred because, even though the Company believes the patents and underlying processes have continuing value, the amount of future benefits to be derived therefrom is uncertain. Purchased patents and licenses are capitalized and amortized on a straight-line basis over the useful life of the patent or license, which range from one to twenty years. When patents reach a mature stage, any associated legal, defense and maintenance costs are expensed as incurred.
	Accrued liabilities – Accrued expenses include accrued payroll, accrued vacation, accrued incentive compensation, accrued royalties, sales and use taxes payable and other various unpaid expenses.
	Accrued liabilities at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Accrued payroll, vacation and employee-related expenses	$	1,024		$	1,173
	Accrued incentive compensation	1,229			612
	Accrued royalties	584			721
	Accrued incentives for sales staff	202			224
	Other	322			420
	Total	$	3,361		$	3,150
	Deferred revenue – Deferred revenue represents payments received, but not yet earned.
	Deferred revenue at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	31-Dec-13			31-Dec-14
	CIRM	$	924		$	3,142
	Coriell	—			189
	Lilly	280			258
	Other	235			329
	Total	$	1,439		$	3,918
	Debt discounts – The Company recorded the fair value of the warrants issued in connection with the Credit Agreement, see Note 5, as a debt discount. The debt discount is amortized to interest expense over a period ending on the earlier of the maturity date of the notes or the date on which the notes are repaid.
	Revenue recognition – The Company recognizes revenue in accordance with Securities and Exchange Commission (SEC) Staff Accounting Bulletin (SAB) No. 104, Revenue Recognition, and Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 605, Revenue Recognition.
	Product sales – The Company recognizes product sales revenue when the following four basic revenue criteria are met: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the fee is fixed or determinable; and (iv) collectability is reasonably assured. Product returns and replacements historically have not been material and are not expected to be material.
	In June 2012, the Company finalized a supply and distribution agreement with Life Technologies Corporation whereby they will manufacture certain cell media for the Company and serve as its sole distributor of these products to third parties. The Company is recognizing this revenue in accordance with ASC 605-45—Revenue Recognition—Principal Agent Consideration. ASC 605-45 specifies various indicators that support the reporting of revenue on a gross basis, including inventory risk, changes to the product and discretion in changing the supplier. The Company does not believe that this agreement includes these characteristics and therefore is recognizing the revenue on a net basis.
	Collaborations, partnerships and other revenues—The Company recognizes revenue from collaborations, services and other arrangements when its contractual services are performed, provided collectability is reasonably assured. Collaborations may include upfront non-refundable payments, development milestone payments and research and development funding. Principal costs under these agreements include the Company’s personnel conducting research and development, supplies consumed in that process and allocated overhead.
	The Company recognizes revenues from non-refundable up-front license fees received under collaboration agreements ratably over the estimated performance period of the collaboration agreement. The estimated performance period is typically based upon detailed project plans completed by the project managers, who establish in regular discussion and collaboration with a counterpart at the customer, key project activities, milestones and resources. If the estimated performance period is subsequently modified, the Company will modify the period over which the up-front license fee is recognized on a prospective basis.
	The Company recognizes revenue from milestone payments received under collaboration agreements when earned, provided that the milestone event is substantive, its achievability was not reasonably assured at the inception of the agreement, the Company has no further performance obligations relating to the event and collectability is reasonably assured. If these criteria are not met, the Company recognizes milestone payments ratably over the remaining period of its performance obligations under the collaboration agreement.
	For a milestone to be considered substantive, the payment associated with its achievement must have all of the following characteristics:
	•	relate solely to past performance;
	•	be reasonable, relative to all of the elements and payment terms in the arrangement; and
	•	be commensurate with either the Company’s effort required to achieve the milestone or the enhanced value of the delivered item(s) as a result of the milestone achievement.
	As of December 31, 2014, the Company has recognized $350,000 of milestone related revenue in association with its contract with Lilly - see Multiple-element arrangements section below. In 2012, the Company sent invoices of $125,000 for milestones achieved. Of the achieved milestones, $25,000 was recognized as revenue in 2012 under the milestone method, while the remaining $100,000, which related to milestones that were not considered substantive, was deferred and accounted for ratably over the remaining period of the Company’s performance obligations under the contract. In 2013 and 2014 the Company recognized $100,000 and $225,000, respectively, of revenue under the milestone method.
	Payments, such as grants or awards, received for the reimbursement of expenses for research and development activities are recorded as revenue at the gross amount of the reimbursement. Costs associated with these reimbursements are reflected as a component of research and development expenses.
	In November, 2013, the Company announced that it had received a Notice of Grant Award (NGA) for $16 million from CIRM to create a human induced pluripotent stem cell biobank from 3,000 individuals. The agreement runs through October 31, 2016. Related to the CIRM grant, in December 2013, the Company announced that it had entered into a four year $6.3 million agreement with Coriell to produce distribution cell banks from the iPSCs produced for CIRM. In accounting for revenue for the agreements mentioned above, the Company will use the Proportional Performance Method whereby revenue will be recognized in proportion to the level of service, as measured by labor and materials cost, provided on a systematic and rational basis. As of December 31, 2014, the Company has received payments totaling $5.8 million from CIRM and has recognized $2.7 million as revenue, resulting in deferred revenue of $3.1 million. As of December 31, 2014, the Company has invoiced Coriell for $651,000 of which $462,000 was recognized as revenue.
Multiple-element arrangements – Arrangements with customers may include multiple deliverables, including collaborations or agreements that combine products, research and development, participation in joint steering committees and other deliverables. For the Company’s multiple-element arrangements, deliverables are separated into more than one unit of accounting when (i) the delivered element(s) have value to the customer on a stand-alone basis and (ii) delivery of the undelivered element(s) is probable and substantially in the control of the Company. Revenue is then allocated to each unit of accounting based on the relative selling price of each unit of accounting based first on Vendor Specific Objective Evidence (“VSOE”) if it exists, based next on Third Party Evidence (“TPE”) if VSOE does not exist, and, finally, if both VSOE and TPE do not exist, based on Best Estimated Selling Price (“BESP”).
VSOE—In many instances, products are sold separately in stand-alone arrangements. The Company determines VSOE based on its normal pricing and discounting practices for the specific product when sold separately.
TPE—When VSOE does not exist, the Company attempts to determine TPE based on competitor prices for similar deliverables when sold separately. Given the novel nature and early stage of the Company’s products, it is difficult to obtain the pricing of similar products with similar functionality sold by other companies on a stand-alone basis. Therefore, the Company is typically not able to determine TPE.
BESP—The objective of BESP is to determine the price at which the Company would transact a sale if the deliverable were sold on a stand-alone basis. When both VSOE and TPE do not exist, typically in the case of research and development and joint steering committee elements, the Company determines BESP by considering the cost of the activities required by the agreement and the rights of the Company and its customers to the resulting technology.
After separating the elements of an arrangement into the appropriate units of accounting, revenue is recognized for each separate unit of accounting based on the nature of the revenue as described above.
In accounting for the multiple-element arrangements, revenue is limited to the lesser of 1) the cumulative amount of payments received or invoiced; or 2) the cumulative amount of revenue earned, as determined using the pro-rata allocation and delivery status or progress of each element.
In June 2012, the Company finalized a $5 million multiple-element agreement with Lilly that was scheduled to run through December 2014. Under the terms of the agreement, Lilly would order a minimum number of units of iCell products each quarter through the fourth quarter of 2014 at a predetermined price for each year. If Lilly failed to order the minimum number of units, the Company could choose a commercial iCell type for the shortfall and invoice Lilly for the same. In addition, through December 31, 2014, the Company also reprogramed a specified number of donor samples provided by Lilly, and invoiced Lilly for these MyCell products according to predetermined pricing tiers. The agreement also included both periodic and milestone payments related to meetings and decisions of a joint steering committee and the custom development of two different cell types.
In December 2012, the Company finalized a one year $1.3 million multiple-element agreement with AstraZeneca UK Limited (AstraZeneca). Under the terms of the agreement, AstraZeneca agreed to order a minimum number of units of commercial iCell products, at a predetermined price, prior to December 31, 2013. During the term, the Company was to reprogram donor samples and invoice AstraZeneca for any such MyCell products. The last of the Company's obligations under this agreement were substantially completed in early 2014. In addition, AstraZeneca agreed to provide the Company with payments upon the achievement of certain milestones related to its attempts to develop, manufacture and commercially release a custom cell type.
Changes in judgments and estimates regarding application of these revenue recognition guidelines as well as changes in facts and circumstances could result in a change in the timing or amount of revenue recognized in future periods. During 2012, 2013 and 2014, the Company did not have any significant changes in estimates related to the agreements discussed above.
Research and development – Research and development costs are expensed as incurred. Research and development costs primarily consist of salaries and other personnel costs, supplies, amortization of patents and licenses, minimum royalties and royalty payments related to Collaborations, partnerships and other revenues and miscellaneous other expenses for facilities and occupancy costs. Other research and development expenses include fees paid to consultants and outside service providers and finished goods used in research and development.
Advertising costs – The Company expenses advertising costs as incurred. The Company incurred advertising costs of $110,000 in 2012, $220,000 in 2013 and $212,000 in 2014.
Stock-based compensation – All share-based payment awards made to employees, consultants (including science advisors) and directors are measured and recognized based on estimated fair values.
Net loss per share of common stock – The Company’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by dividing the net loss by the weighted-average number of potential common shares outstanding for the period determined using the treasury-stock method. For purposes of this calculation, the following potential common shares were excluded because including them would have been anti-dilutive:
		December 31,
		2012		2013			2014
Preferred series A		2,914,187		—			—
Preferred series B		7,232,092		—			—
Common stock warrants		8,208		28,406			28,406
Common stock options		1,617,875		2,388,394			2,759,770
		11,772,362		2,416,800			2,788,176
Comprehensive loss – Comprehensive loss is equal to net loss as presented in the accompanying statements of operations.
Segment reporting – ASC 280, “Segment Reporting” requires use of the “management approach” model for segment reporting. The management approach model is based on the way a company’s management organizes segments within the company for making operating decisions and assessing performance. The Company determined it has one operating segment. Disaggregation of the Company’s operating results is impracticable, because the Company’s research and development activities and its assets overlap, and management reviews its business as a single operating segment. Thus, discrete financial information is not available by more than one operating segment.
Product information – The following table provides Product sales revenue by product:
		Year ended
		December 31,
(Dollars in thousands)		2012		2013			2014
iCell Cardiomyocytes		$2,610		$4,787			$3,175
iCell Neurons		2,256		2,428			3,317
MyCell		—		222			857
Other		312		561			728
Total		$5,178		$7,998			$8,077
Collaborations, partnerships and other revenue information - The following table provides Collaborations, partnerships and other revenues by significant agreement or type:
		Year ended
		December 31,
(Dollars in thousands)		2012			2013				2014
CIRM/Coriell		$	—		$	182			$	3,008
MCOW		440			533				1,144
Collaborative cell development		728			1,857				1,287
iCell Hepatocytes		127			808				1,796
Prototype cells		—			381				777
Other		109			125				603
Total		$	1,404		$	3,886			$	8,615
Geographical information – The following table provides percentage of total revenues by region, based on shipping locations or, in the case of CIRM, the customer location:
		Year ended
		December 31,
		2012		2013			2014
United States of America		66	%	56	%		67	%
Europe		24	%	38	%		28	%
Japan		5	%	5	%		4	%
Other		5	%	1	%		1	%
Total		100	%	100	%		100	%
In 2012 outside of the United States of America, no country accounted for over 10% of revenues. In 2013, sales to customers in the United Kingdom accounted for 12% of total revenue, while sales to customers in Switzerland accounted for 11% of total revenue. In 2014, sales to customers in Switzerland accounted for 15% of total revenue.
Major customers – During 2012, 2013 and 2014, the Company had several large biopharmaceutical customers that individually accounted for greater than 10% of its total revenue in one or more of the periods. Lilly accounted for 18% and 18% of total revenue for both 2012 and 2013. GlaxoSmithKline plc accounted for 11% of total revenue in 2012. AstraZeneca accounted for 15% of total revenue in 2013. Hoffman-La Roche Inc. (Roche) and CIRM accounted for 10% and 15%, respectively, of total revenue in 2014.
As of December 31, 2013, receivables from Lilly, AstraZeneca and Roche accounted for 21%, 17% and 11%, respectively, of total accounts receivable. As of December 31, 2014, receivables from Lilly, Roche and the Medical College of Wisconsin (MCOW) accounted for 16%, 15% and 13%, respectively, of total accounts receivable.
Concentration of credit risk and other risks and uncertainties – As of December 31, 2014 the Company had $24.6 million invested in a 100% U.S. Treasury Securities Money Market Fund and $1.9 million in a U.S. Government Money Market Fund. An investment in a money market fund is not insured or guaranteed. The Company's remaining cash was deposited with one major financial institution. These deposits exceed federally insured limits. The Company has not experienced any losses in such accounts and believes that the Company is not exposed to any significant risk on these balances.
The Company is currently not profitable and no assurance can be provided that it will ever be profitable. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, dependence on key personnel, dependence on key suppliers, protection of proprietary technology, the validity of and continued access to its owned and licensed intellectual property, compliance with government regulations, uncertainty of widespread market acceptance of products and the need to obtain additional financing. The Company's products include materials subject to rapid technological change. Certain materials used in manufacturing have relatively few alternative sources of supply and establishing additional or replacement suppliers for such materials cannot be accomplished quickly. While the Company has ongoing programs to minimize the adverse effect of such uncertainty, and the Company considers technological change in estimating allowances, uncertainty continues to exist.
The Company believes its cash balance is sufficient to meet its needs in 2015. However, it may need to raise additional capital to expand the commercialization of its products, fund its operations and further its research and development activities.
Fair value of financial instruments – The carrying amounts of financial instruments, which include cash and cash equivalents, accounts receivable and accounts payable, approximate their respective fair values due to the relatively short-term nature of these instruments. The Company believes the carrying value of long-term debt as of December 31, 2014 is also approximately equal to its fair value.
ASC Topic 820, Fair Value Measurement, establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include Level 1, defined as observable inputs, such as quoted market prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore, requiring an entity to develop its own assumptions. The Company uses the market approach and Level 1 inputs to value its cash equivalents.
Recent accounting pronouncements – In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entities Ability to Continue as a Going Concern "ASU No. 2014-15", which is included in Accounting Standards Codification 205, Presentation of Financial Statements. ASU No. 2014-15 requires management to assess an entity's ability to continue as a going concern, and to provide related footnote disclosure in certain circumstances. ASU No. 2014-15 will be effective for the Company starting in the first quarter of fiscal year 2017. Early application is permitted. The Company is currently evaluating the impact the adoption of ASU No. 2014-15 will have on its financial statements.
In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers "ASU No. 2014-09", which supersedes nearly all accounting standards for revenue recognition. ASU No. 2014-09 requires that an entity recognize revenue upon transferring promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU No. 2014-09 will be effective for the Company starting in the first quarter of fiscal year 2017. Early application is not permitted. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact the adoption of ASU No. 2014-09 will have on its financial statements.

Intangible_assets

Intangible assets	12 Months Ended
	Dec. 31, 2014
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible assets
	4	Intangible assets
	Intangible assets and accumulated amortization balances at December 31, 2013 and December 31, 2014, are as follows:
	(dollars in thousands)	December 31,			December 31,
		2013			2014
	Trade name	$	13		$	13
	Licenses and patents	4,578			4,722
	Non-competition agreements	641			761
		5,232			5,496
	Less accumulated amortization:
	Trade name	(13		)	(13		)
	Licenses and patents	(746		)	(1,152		)
	Non-competition agreements	(351		)	(518		)
		(1,110		)	(1,683		)
	Total, net	$	4,122		$	3,813
	As of December 31, 2013 and 2014, the trade name was fully amortized. The remaining weighted-average useful lives of the other intangible assets as of December 31, 2014 are as follows:
	Licenses and patents	11.8 years
	Non-competition agreements	5.2 years
	The future amortization of intangible assets recorded as of December 31, 2014 is as follows:
	(Dollars in thousands)
	Years ending December 31,	Amount
	2015	$	564
	2016	428
	2017	385
	2018	333
	2019	330
	Thereafter	1,773
		$	3,813
	Amortization expense was $347,000, $522,000 and $584,000 for 2012, 2013 and 2014, respectively.
	A portion of the July 30, 2013 stock option grant to a scientific founder of the Company was issued in exchange for extending his non-competition agreement from December of 2015 to July of 2016. As of the grant date, the Company increased the value of the non-competition agreement by $70,000 and began amortizing that amount through July of 2016. A portion of a March 2014 stock option grant made to the same scientific founder of the Company was issued in exchange for extending his non-competition agreement from July 2016 to July 2017. As of the grant date, the Company increased the value of the non-competition agreement by $120,000 and began amortizing that amount through July 2017.

Longterm_debt

Long-term debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Long-term debt
	5	Long-term debt
	Long-term debt at December 31, 2013 and 2014, consists of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Term loan credit agreement, net of debt discount	$	11,879		$	12,131
	License agreements	18			—
		11,897			12,131
	Less current portion	(18		)	(4,541		)
	Total	$	11,879		$	7,590
	On June 27, 2013, the Company entered into a term loan credit agreement (the “Credit Agreement”) with Sixth Floor Investors LP ("Sixth Floor"), as administrative agent, and the other lenders party thereto (the “Lenders”). Under the Credit Agreement, on June 28, 2013, the Company borrowed $12.0 million.
	The term of the Credit Agreement is four years. Outstanding balances bear interest at 6.5% per annum plus the greater of 2% or one-month LIBOR. Interest payments are made monthly in arrears. Principal will be payable in 30 monthly installments, beginning in February 2015. The Credit Agreement provides for an exit fee of 5.0% of the total amount borrowed under the facility, due upon final repayment; a 0.5% facility fee, which was paid upon execution of the Credit Agreement; a quarterly administrative fee of $2,500; and the reimbursement of certain fees and expenses of the Lenders. In the event of prepayment, other than regularly scheduled installments and mandatory prepayments, a premium of 1.0% to 2.0% of the then-outstanding balance, dependent upon the timing of the prepayment, would be incurred.
	The Credit Agreement does not allow the Company to incur or permit to exist additional debt, except for liabilities arising with respect to customary indemnification contracts entered into in the ordinary course of business. The Company used a portion of the proceeds of the loan to repay the remaining balances due to the Wisconsin Economic Development Corporation under two promissory notes.
	The Credit Agreement contains customary affirmative and negative covenants and events of default, but does not include financial covenants. The Credit Agreement restricts the Company’s ability to, among other things, sell certain assets, engage in a merger or change in control transaction, incur debt, pay cash dividends, enter into transactions with affiliates and make investments. The Credit Agreement also contains events of default that are customary for credit facilities of this type, including payment defaults, covenant defaults, defaults related to insolvency and events of default relating to liens, judgments, material misrepresentations and the occurrence of certain material adverse events.
	In connection with the loan, the Lenders were issued detachable warrants to purchase shares of our Series B preferred stock. The warrants have since been converted to warrants to purchase shares of common stock, see Note 6. A total of 28,406 warrants were issued in respect of the loan, each with an exercise price per share equal to the initial public offering ("IPO") price per share in the Company's initial public offering or $12.68 if an offering was not completed before August 1, 2013. As of the date of our IPO, the strike price on these warrants was established at the IPO price per share of $12.00.
	The warrants have a 10 year term. The warrants contain no mandatory redemption features and no repurchase obligations requiring the transferring of assets and, once issued, will relate to a fixed number of shares, except for customary anti-dilution adjustments.
	At the time of issuance, the relative fair value of the warrants was estimated at $261,000 using the Black- Scholes method and recorded as a debt discount against the notes. The warrants had a strike price that would have been adjusted if the Company had not completed its initial public offering prior to August 1, 2013. Due to this initial variability in exercise price, the warrants were accounted for as a liability when issued. As of the IPO date, when the exercise price was no longer variable, the Company revalued the warrants and reclassified the remaining value to equity. The revaluation resulted in a $20,000 gain that was recorded to Other income in the statements of operations.

Shareholders_equity

Shareholders' equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Stockholders' equity
	6	Shareholders' equity
	On July 30, 2013, the Company closed its IPO of 3,846,000 shares of its common stock. The public offering price of the shares sold in the offering was $12.00 per share. The total gross proceeds from the offering to the Company were $46.2 million. After deducting underwriting discounts and commissions and offering expenses payable by the Company, the aggregate net proceeds received by the Company totaled approximately $40.8 million.
	Immediately prior to the consummation of the IPO, all outstanding shares of Series A and Series B preferred stock were converted into shares of common stock on a one-for-one basis, and warrants to purchase Series B preferred stock were converted into warrants to purchase shares of common stock on a one-for-one basis. In addition, in connection with the IPO, warrants to purchase 8,208 shares of common stock were exercised at a strike price of $0.10 per share.
	In connection with the IPO, the Company amended and restated its articles of incorporation to authorize 100,000,000 shares of common stock and 10,000,000 shares of preferred stock. As of December 31, 2014, no shares of preferred stock have been issued.

Stock_options_and_restricted_c

Stock options and restricted common stock	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock options and restricted common stock	7.    Stock options and restricted common stock
	The Company's board of directors adopted and its shareholders approved the 2013 Equity Incentive Plan (the “2013 Plan”), under which the Company approved option grants to its directors and executive officers. The 2013 Plan and these option grants became effective on the closing of the IPO. As of that same date, the Company discontinued the granting of options under the 2008 Equity Incentive Plan (the "2008 Plan").
	The options are contingent on the participants' continued employment or other service and are subject to forfeiture if employment terminates for any reason. To date, the Company has granted both incentive stock options and non-qualified stock options. The 2008 Plan and 2013 Plan also provide certain employees accelerated vesting in the event of changes in control.
	The Company utilizes the Black-Scholes option-pricing model to determine the fair value of option grants. When the option grants have the characteristics of a "plain-vanilla" grant the expected term is based on the simplified method as prescribed by Staff Accounting Bulletin ("SAB") No. 107 and SAB No. 110. In the event that the options do not have such characteristics the Company bases the expected term on items such as expiration dates and other factors unique to the grantee. The risk-free interest rate assumptions are based on the U.S. Treasury bond rates appropriate for the expected term in effect at the time of grant. The expected volatility is based on calculated enterprise value volatilities for publicly traded companies in the same industry and general stage of development. The forfeiture rates are based on historical experience for similar classes of employees. The dividend yield is based on expected dividends at the time of grant. Prior to the Company's IPO, the determinations of fair values were based on, among other things, valuation analyses, review of historical financial results, business milestones, financial forecasts and business outlook as of the grant dates. Total enterprise value ranges and the total equity value ranges were estimated utilizing both the income approach and the market approach guidelines. Upon completion of the IPO the common stock was valued by reference to the Company's publicly traded price.
	Assumptions used to value the most recent option grants were as follows:
		2012		2013		2014
	Estimated expected term	6 years		6 to 8 years		1 to 8 years
	Risk-free interest rate	0.98	%	1.70% to 2.22%		0.18% to 2.38%
	Expected volatility assumption	66	%	64% to 68%		43% to 66%
	Forfeiture rate	0% to 7%		0% to 7%		0% to 6%
	Dividend yield assumption	—	%	—	%	—	%
	Option awards to consultants, advisors or other independent contractors have been granted with an exercise price equal to the market price of the Company’s stock at the date of the grant, with 10-year contractual terms and vesting dependent upon whether the individual continues to provide services to the Company. The value of stock options to these parties is measured at the then-current market value as of financial reporting dates and compensation cost is recognized for the net change in the fair value of the options for the reporting period, until vesting terms are met. In determining the fair value of options granted to consultants, advisors and other independent contractors, the Company uses the Black-Scholes valuation model in a manner consistent with its use in determining the fair value of options granted to employees and directors. The options that vest are adjusted, for the last time, to the then-current fair value and compensation cost is recognized accordingly.
	The number of shares available for grant under the Company's Equity Incentive Plans, as amended (the "Plans") were as follows:
		2008 Plan		2013 Plan		Total
	Available for grant — January 1, 2012	243,665		—		243,665
	Plan amendment	262,256		—		262,256
	Grants	(99,187	)	—		(99,187	)
	Forfeitures	6,954		—		6,954
	Available for grant — December 31, 2012	413,688		—		413,688
	Plan adjustments and amendments	(421,371	)	831,659		410,288
	Grants	—		(812,116	)	(812,116	)
	Forfeitures	7,683		10,327		18,010
	Available for grant — December 31, 2013	—		29,870		29,870
	Plan adjustments and amendments	(84,494	)	630,309		545,815
	Grants	—		(599,311	)	(599,311	)
	Forfeitures	84,494		87,158		171,652
	Available for grant — December 31, 2014	—		148,026		148,026
	A summary of option activity under the Plans as of December 31, 2014 and changes during the period then ended were as follows:
		Options		Weighted-			Weighted-
				average			average
				exercise			remaining
				price			contractual
							term
	Outstanding — January 1, 2012	1,545,938		$	8.09		8.42
	Granted	99,187		12.68
	Exercised	(20,296	)	7.41
	Forfeited	(6,954	)	12.19
	Outstanding — December 31, 2012	1,617,875		8.39			7.63
	Granted	812,116		12.31
	Exercised	(23,587	)	6.55
	Forfeited	(18,010	)	11.34
	Outstanding — December 31, 2013	2,388,394		9.7			7.63
	Granted	599,311		14.54
	Exercised	(56,283	)	6.14
	Forfeited	(171,652	)	11.33
	Outstanding — December 31, 2014	2,759,770		$	10.72		7.14
	Vested as of December 31, 2014	1,641,991		$	8.86		6.14
	Vested or expected to vest as of December 31, 2014	2,746,571		$	10.71		7.13
	Exercisable as of December 31, 2014	1,779,870		$	9.16		6.23
	Under the terms of the 2008 Plan, option grants are immediately exercisable. If a participant exercises unvested options, the shares received from the exercise are considered restricted shares and the participant's rights thereto remain subject to the original vesting schedule of the options. At December, 31, 2012, 2013 and 2014 there were no such restricted shares. Under the terms of the 2013 Plan, options are not exercisable until vested.
	The weighted-average grant-date fair value of stock options granted during 2012, 2013 and 2014 was $4.10, $8.31 and $9.65 per share, respectively. The aggregate intrinsic value of outstanding stock options was $70,000 as of December 31, 2014. At December 31, 2014 total compensation cost not yet recognized that related to nonvested awards was $7.1 million, which was expected to be recognized over a weighted-average period of 2.77 years. That amount excludes options issued in exchange for and accounted as intangible assets. See Note 4.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The Company recognizes deferred tax assets and liabilities for both the expected impact of differences between the financial statements and the tax basis of assets and liabilities, and for the expected future tax benefit to be derived from tax losses and tax credit carryforwards. Deferred tax balances primarily relate to net operating losses. The Company also established a valuation allowance to reflect the likelihood of realization of deferred tax assets. Realization of deferred tax assets, including those related to the U.S. net operating loss carryforwards, are dependent upon future earnings, if any, of which the timing and amount are uncertain.
	As of December 31, 2014, the Company has net operating loss carryforwards for tax purposes of approximately $130.0 million for federal and $97.0 million for state. These federal net operating losses begin to expire in 2024 and the state net operating losses begin to expire in 2019. The carryforwards are subject to the Internal Revenue Code Section 382, which places a limitation on the amount of taxable income that can be offset by net operating losses after a change in ownership. In addition, the Company has federal tax credit carryforwards of $3.3 million and state tax credits of $4.5 million. The credits begin to expire in 2025 and 2016, respectively.
	The components of the net deferred tax asset with the approximate income tax effect of each type of carryforward, credit and temporary differences are as follows.
	(Dollars in thousands)	31-Dec-13				31-Dec-14
	Deferred tax assets
	Operating loss carryforwards	$	41,141			$	50,387
	Tax credit carryforwards	5,529				6,290
	Other temporary differences	2,327				3,599
	Tax assets before valuation allowance	48,997				60,276
	Less: valuation allowance	(48,997		)		(60,276		)
	Net deferred taxes	$	—			$	—
	A valuation allowance to reduce the deferred tax assets is reported if, based on the weight of the evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company has incurred significant losses since its inception and due to the uncertainty of the amount and timing of future taxable income, management has determined that a $49.0 million and $60.3 million valuation allowance at December 31, 2013 and 2014, respectively, is necessary to reduce the tax assets to the amount that is more likely than not to be realized.
	The effective tax rate differs from the statutory tax rate due to the following:
		Year ended December 31,
		2012			2013			2014
	U.S. Federal statutory rate	35	%		35	%		35	%
	State taxes	5			5			1.3
	Research credits	—			13.3			2.5
	Stock-based compensation	(0.5	)		(0.5	)		(0.1	)
	Other	(0.2	)		(0.1	)		(0.2	)
	Valuation allowance	(39.3	)		(52.7	)		(38.5	)
		—	%		—	%		—	%
	The Company has evaluated uncertain tax positions as of December 31, 2013 and 2014 and determined a reserve for such positions and any associated interest and penalties is not necessary.
	All of the Company's tax years are subject to examination by the U.S. and state tax authorities due to the carryforward of unutilized net operating losses.
	The Company does not expect there will be a change in the unrecognized tax benefits within the 12 months following December 31, 2014.

401k_savings_plan_401k_savings

401(k) savings plan 401(k) savings plan	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
401(k) savings plan	9.    401(k) savings plan
	The Company has established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code (the plan). The plan covers substantially all employees. Under the plan, employees may make elective salary deferrals. In 2012, 2013 and 2014 the Company matched $48,000, $53,000 and $63,000, respectively, of employee contributions.

Commitments_and_contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies
	Operating leases – The Company leases corporate office space, office equipment and production facilities under operating leases. Total rent payments were $577,000 for 2012, $823,000 for 2013 and $949,000 for 2014.
	Future minimum lease payments at December 31, 2014, under operating leases with initial or remaining terms in excess of one year were as follows:
	(Dollars in thousands)
	Years ending December 31,
	2015	$	942
	2016	932
	2017	841
	2018	512
	2019	16
	Thereafter	—
		$	3,243
	Contingencies – From time to time, the Company may be subject to various legal proceedings and claims arising in the ordinary course of business. The Company assesses contingencies to determine the degree of probability and range of possible loss for potential accrual in its financial statements. An estimated loss contingency is accrued in the financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. No such amounts were accrued at December 31, 2013 or December 31, 2014.

Relatedparty_transactions

Related-party transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related-party transactions
	11	Related-party transactions
	The Company has consulting agreements with scientific advisors who are also shareholders. The total expense recorded to general and administrative expenses for these agreements was $302,000 for 2012, 2013 and 2014.
	In July 2013 and in March 2014, the Company granted stock options in exchange for future services and amendments to consulting and non-competition agreements with a scientific founder of the Company who also serves on the board of directors. See Note 4 for additional information.

Significant_accounting_policie1

Significant accounting policies and supplemental financial information (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Presentation and use of estimates	Basis of presentation and use of estimates – The accompanying financial statements have been presented in conformity with accounting principles generally accepted in the United States of America (GAAP). The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions include primarily those required in the valuation of inventory, patents, licenses, goodwill, intangible assets, and property and equipment; the timing of revenue recognition; and the calculation of stock-based compensation. Management bases its estimates on certain assumptions, which it believes are reasonable in the circumstances, and while actual results could differ from those estimates, management does not believe that any change in those assumptions in the near term would have a significant effect on the Company’s financial position, results of operations or cash flows.
Cash and cash equivalents	Cash and cash equivalents – The Company considers all highly liquid, short-term investments with original maturities of three months or less to be cash and cash equivalents.
Accounts receivable	Accounts receivable – The Company establishes an allowance for doubtful accounts based on a customer's ability and likelihood to pay. There was no allowance at either December 31, 2013 or December 31, 2014.
	The Company does not accrue interest on past due amounts. Past due accounts are determined based on customer terms, the policy for write-offs and collection efforts is based upon individual account circumstances.
Inventories	Inventories – Inventories are valued at the lower of cost or market using the weighted-average cost method. The weighted-average method examines total production volume and total labor and overhead over an appropriate historical period and establishes a weighted-average value of materials, overhead and labor to be assigned to each unit of finished goods inventory.
	Inventory includes finished goods that may be used by the Company’s research and development, technical services and marketing groups. When such products are consumed internally they are expensed at their inventoried cost to the appropriate department.
	Provisions, when required, for slow moving, excess and obsolete inventories are recorded to reduce inventory values from cost to their estimated net realizable values, based on product life cycle, development plans, product expiration and quality issues.
Prepaid expenses and other current assets	Prepaid expenses and other current assets – Prepaid expenses and other current assets consist of insurance premiums, annual maintenance contracts and other miscellaneous payments and deposits.
Property and equipment	Property and equipment – Property and equipment are recorded at cost and are depreciated using the straight-line method over the useful life of the assets, which is three to seven years. Leasehold improvements are depreciated over the shorter of their estimated useful life or the lease term.
Impairment of long-lived assets	Impairment of long-lived assets – The Company reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be fully recoverable. An impairment loss would be recognized when the estimated future cash flows from the use of the asset are less than the carrying amount of that asset. No impairment losses were recorded in either 2013 or 2014.
Goodwill	Goodwill – The entire balance of goodwill resulted from the 2008 acquisition of two companies and represents the purchase price in excess of identifiable assets and in-process research and development acquired in that transaction. Goodwill is not amortized.  The Company has a single reporting unit and all goodwill relates to that unit.
	Goodwill, which has an indefinite useful life, represents the excess of cost over fair value of net assets acquired. Goodwill is reviewed for impairment at least annually during the fourth quarter, or more frequently if an event occurs indicating the potential for impairment. The Company conducts an assessment of qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the Company determines that it is more likely than not that the fair value of its reporting unit is less than its carrying amount, it then conducts a two-part test for impairment of goodwill. The qualitative factors which the Company may assess during the qualitative approach include, but are not limited to, macroeconomic conditions, industry and market considerations, the overall financial performance of the Company, and the excess of prior year estimates of fair value compared to carrying value. Based on this qualitative assessment, management concluded that as of the 2014 annual impairment test date, it was more likely than not that the fair value of the reporting unit was greater than its carrying value, and no further testing was performed.
Intangible assets	Intangible assets – Intangible assets consist of licenses, patents, trade name and a noncompetition agreement with a scientific founder.
	The Company expenses patent related costs as incurred because, even though the Company believes the patents and underlying processes have continuing value, the amount of future benefits to be derived therefrom is uncertain. Purchased patents and licenses are capitalized and amortized on a straight-line basis over the useful life of the patent or license, which range from one to twenty years. When patents reach a mature stage, any associated legal, defense and maintenance costs are expensed as incurred.
Accrued liabilities	Accrued liabilities – Accrued expenses include accrued payroll, accrued vacation, accrued incentive compensation, accrued royalties, sales and use taxes payable and other various unpaid expenses.
Deferred revenue	Deferred revenue – Deferred revenue represents payments received, but not yet earned.
Debt Discounts	Debt discounts – The Company recorded the fair value of the warrants issued in connection with the Credit Agreement, see Note 5, as a debt discount. The debt discount is amortized to interest expense over a period ending on the earlier of the maturity date of the notes or the date on which the notes are repaid.
Revenue recognition	Revenue recognition – The Company recognizes revenue in accordance with Securities and Exchange Commission (SEC) Staff Accounting Bulletin (SAB) No. 104, Revenue Recognition, and Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 605, Revenue Recognition.
	Product sales – The Company recognizes product sales revenue when the following four basic revenue criteria are met: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the fee is fixed or determinable; and (iv) collectability is reasonably assured. Product returns and replacements historically have not been material and are not expected to be material.
	In June 2012, the Company finalized a supply and distribution agreement with Life Technologies Corporation whereby they will manufacture certain cell media for the Company and serve as its sole distributor of these products to third parties. The Company is recognizing this revenue in accordance with ASC 605-45—Revenue Recognition—Principal Agent Consideration. ASC 605-45 specifies various indicators that support the reporting of revenue on a gross basis, including inventory risk, changes to the product and discretion in changing the supplier. The Company does not believe that this agreement includes these characteristics and therefore is recognizing the revenue on a net basis.
	Collaborations, partnerships and other revenues—The Company recognizes revenue from collaborations, services and other arrangements when its contractual services are performed, provided collectability is reasonably assured. Collaborations may include upfront non-refundable payments, development milestone payments and research and development funding. Principal costs under these agreements include the Company’s personnel conducting research and development, supplies consumed in that process and allocated overhead.
	The Company recognizes revenues from non-refundable up-front license fees received under collaboration agreements ratably over the estimated performance period of the collaboration agreement. The estimated performance period is typically based upon detailed project plans completed by the project managers, who establish in regular discussion and collaboration with a counterpart at the customer, key project activities, milestones and resources. If the estimated performance period is subsequently modified, the Company will modify the period over which the up-front license fee is recognized on a prospective basis.
	The Company recognizes revenue from milestone payments received under collaboration agreements when earned, provided that the milestone event is substantive, its achievability was not reasonably assured at the inception of the agreement, the Company has no further performance obligations relating to the event and collectability is reasonably assured. If these criteria are not met, the Company recognizes milestone payments ratably over the remaining period of its performance obligations under the collaboration agreement.
	For a milestone to be considered substantive, the payment associated with its achievement must have all of the following characteristics:
	•	relate solely to past performance;
	•	be reasonable, relative to all of the elements and payment terms in the arrangement; and
	•	be commensurate with either the Company’s effort required to achieve the milestone or the enhanced value of the delivered item(s) as a result of the milestone achievement.
	As of December 31, 2014, the Company has recognized $350,000 of milestone related revenue in association with its contract with Lilly - see Multiple-element arrangements section below. In 2012, the Company sent invoices of $125,000 for milestones achieved. Of the achieved milestones, $25,000 was recognized as revenue in 2012 under the milestone method, while the remaining $100,000, which related to milestones that were not considered substantive, was deferred and accounted for ratably over the remaining period of the Company’s performance obligations under the contract. In 2013 and 2014 the Company recognized $100,000 and $225,000, respectively, of revenue under the milestone method.
	Payments, such as grants or awards, received for the reimbursement of expenses for research and development activities are recorded as revenue at the gross amount of the reimbursement. Costs associated with these reimbursements are reflected as a component of research and development expenses.
	In November, 2013, the Company announced that it had received a Notice of Grant Award (NGA) for $16 million from CIRM to create a human induced pluripotent stem cell biobank from 3,000 individuals. The agreement runs through October 31, 2016. Related to the CIRM grant, in December 2013, the Company announced that it had entered into a four year $6.3 million agreement with Coriell to produce distribution cell banks from the iPSCs produced for CIRM. In accounting for revenue for the agreements mentioned above, the Company will use the Proportional Performance Method whereby revenue will be recognized in proportion to the level of service, as measured by labor and materials cost, provided on a systematic and rational basis. As of December 31, 2014, the Company has received payments totaling $5.8 million from CIRM and has recognized $2.7 million as revenue, resulting in deferred revenue of $3.1 million. As of December 31, 2014, the Company has invoiced Coriell for $651,000 of which $462,000 was recognized as revenue.
	Multiple-element arrangements – Arrangements with customers may include multiple deliverables, including collaborations or agreements that combine products, research and development, participation in joint steering committees and other deliverables. For the Company’s multiple-element arrangements, deliverables are separated into more than one unit of accounting when (i) the delivered element(s) have value to the customer on a stand-alone basis and (ii) delivery of the undelivered element(s) is probable and substantially in the control of the Company. Revenue is then allocated to each unit of accounting based on the relative selling price of each unit of accounting based first on Vendor Specific Objective Evidence (“VSOE”) if it exists, based next on Third Party Evidence (“TPE”) if VSOE does not exist, and, finally, if both VSOE and TPE do not exist, based on Best Estimated Selling Price (“BESP”).
	VSOE—In many instances, products are sold separately in stand-alone arrangements. The Company determines VSOE based on its normal pricing and discounting practices for the specific product when sold separately.
	TPE—When VSOE does not exist, the Company attempts to determine TPE based on competitor prices for similar deliverables when sold separately. Given the novel nature and early stage of the Company’s products, it is difficult to obtain the pricing of similar products with similar functionality sold by other companies on a stand-alone basis. Therefore, the Company is typically not able to determine TPE.
	BESP—The objective of BESP is to determine the price at which the Company would transact a sale if the deliverable were sold on a stand-alone basis. When both VSOE and TPE do not exist, typically in the case of research and development and joint steering committee elements, the Company determines BESP by considering the cost of the activities required by the agreement and the rights of the Company and its customers to the resulting technology.
	After separating the elements of an arrangement into the appropriate units of accounting, revenue is recognized for each separate unit of accounting based on the nature of the revenue as described above.
	In accounting for the multiple-element arrangements, revenue is limited to the lesser of 1) the cumulative amount of payments received or invoiced; or 2) the cumulative amount of revenue earned, as determined using the pro-rata allocation and delivery status or progress of each element.
	In June 2012, the Company finalized a $5 million multiple-element agreement with Lilly that was scheduled to run through December 2014. Under the terms of the agreement, Lilly would order a minimum number of units of iCell products each quarter through the fourth quarter of 2014 at a predetermined price for each year. If Lilly failed to order the minimum number of units, the Company could choose a commercial iCell type for the shortfall and invoice Lilly for the same. In addition, through December 31, 2014, the Company also reprogramed a specified number of donor samples provided by Lilly, and invoiced Lilly for these MyCell products according to predetermined pricing tiers. The agreement also included both periodic and milestone payments related to meetings and decisions of a joint steering committee and the custom development of two different cell types.
	In December 2012, the Company finalized a one year $1.3 million multiple-element agreement with AstraZeneca UK Limited (AstraZeneca). Under the terms of the agreement, AstraZeneca agreed to order a minimum number of units of commercial iCell products, at a predetermined price, prior to December 31, 2013. During the term, the Company was to reprogram donor samples and invoice AstraZeneca for any such MyCell products. The last of the Company's obligations under this agreement were substantially completed in early 2014. In addition, AstraZeneca agreed to provide the Company with payments upon the achievement of certain milestones related to its attempts to develop, manufacture and commercially release a custom cell type.
	Changes in judgments and estimates regarding application of these revenue recognition guidelines as well as changes in facts and circumstances could result in a change in the timing or amount of revenue recognized in future periods. During 2012, 2013 and 2014, the Company did not have any significant changes in estimates related to the agreements discussed above.
Research and development	Research and development – Research and development costs are expensed as incurred. Research and development costs primarily consist of salaries and other personnel costs, supplies, amortization of patents and licenses, minimum royalties and royalty payments related to Collaborations, partnerships and other revenues and miscellaneous other expenses for facilities and occupancy costs. Other research and development expenses include fees paid to consultants and outside service providers and finished goods used in research and development.
Advertising costs	Advertising costs – The Company expenses advertising costs as incurred.
Stock-based compensation	Stock-based compensation – All share-based payment awards made to employees, consultants (including science advisors) and directors are measured and recognized based on estimated fair values.
Net loss per share of common stock	Net loss per share of common stock – The Company’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by dividing the net loss by the weighted-average number of potential common shares outstanding for the period determined using the treasury-stock method.
Comprehensive loss	Comprehensive loss – Comprehensive loss is equal to net loss as presented in the accompanying statements of operations.
Segment reporting	Segment reporting – ASC 280, “Segment Reporting” requires use of the “management approach” model for segment reporting. The management approach model is based on the way a company’s management organizes segments within the company for making operating decisions and assessing performance. The Company determined it has one operating segment. Disaggregation of the Company’s operating results is impracticable, because the Company’s research and development activities and its assets overlap, and management reviews its business as a single operating segment. Thus, discrete financial information is not available by more than one operating segment.
Concentration of credit risk and other risks and uncertainties	Concentration of credit risk and other risks and uncertainties – As of December 31, 2014 the Company had $24.6 million invested in a 100% U.S. Treasury Securities Money Market Fund and $1.9 million in a U.S. Government Money Market Fund. An investment in a money market fund is not insured or guaranteed. The Company's remaining cash was deposited with one major financial institution. These deposits exceed federally insured limits. The Company has not experienced any losses in such accounts and believes that the Company is not exposed to any significant risk on these balances.
	The Company is currently not profitable and no assurance can be provided that it will ever be profitable. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, dependence on key personnel, dependence on key suppliers, protection of proprietary technology, the validity of and continued access to its owned and licensed intellectual property, compliance with government regulations, uncertainty of widespread market acceptance of products and the need to obtain additional financing. The Company's products include materials subject to rapid technological change. Certain materials used in manufacturing have relatively few alternative sources of supply and establishing additional or replacement suppliers for such materials cannot be accomplished quickly. While the Company has ongoing programs to minimize the adverse effect of such uncertainty, and the Company considers technological change in estimating allowances, uncertainty continues to exist.
Fair value of financial instruments	Fair value of financial instruments – The carrying amounts of financial instruments, which include cash and cash equivalents, accounts receivable and accounts payable, approximate their respective fair values due to the relatively short-term nature of these instruments. The Company believes the carrying value of long-term debt as of December 31, 2014 is also approximately equal to its fair value.
	ASC Topic 820, Fair Value Measurement, establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include Level 1, defined as observable inputs, such as quoted market prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore, requiring an entity to develop its own assumptions. The Company uses the market approach and Level 1 inputs to value its cash equivalents.
Recent accounting pronouncements	Recent accounting pronouncements – In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entities Ability to Continue as a Going Concern "ASU No. 2014-15", which is included in Accounting Standards Codification 205, Presentation of Financial Statements. ASU No. 2014-15 requires management to assess an entity's ability to continue as a going concern, and to provide related footnote disclosure in certain circumstances. ASU No. 2014-15 will be effective for the Company starting in the first quarter of fiscal year 2017. Early application is permitted. The Company is currently evaluating the impact the adoption of ASU No. 2014-15 will have on its financial statements.
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers "ASU No. 2014-09", which supersedes nearly all accounting standards for revenue recognition. ASU No. 2014-09 requires that an entity recognize revenue upon transferring promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU No. 2014-09 will be effective for the Company starting in the first quarter of fiscal year 2017. Early application is not permitted. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact the adoption of ASU No. 2014-09 will have on its financial statements.

Significant_accounting_policie2

Significant accounting policies and supplemental financial information (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Schedule of Inventory	Inventories at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Raw materials	$	1,658		$	1,598
	Work in process	547			436
	Finished goods	1,679			2,422
	Total	$	3,884		$	4,456
Schedule of Property and equipment	Property and equipment at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Leasehold improvements	$	451		$	835
	Production and lab equipment	4,815			7,274
	Office and computer equipment	546			1,354
	Construction-in-progress	932			162
		6,744			9,625
	Less accumulated depreciation and amortization	(4,692		)	(5,793		)
	Total	$	2,052		$	3,832
Schedule of Accrued liabilities	Accrued liabilities at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Accrued payroll, vacation and employee-related expenses	$	1,024		$	1,173
	Accrued incentive compensation	1,229			612
	Accrued royalties	584			721
	Accrued incentives for sales staff	202			224
	Other	322			420
	Total	$	3,361		$	3,150
Schedule of Deferred Revenue	Deferred revenue at December 31, 2013 and December 31, 2014, consisted of the following:
	(Dollars in thousands)	31-Dec-13			31-Dec-14
	CIRM	$	924		$	3,142
	Coriell	—			189
	Lilly	280			258
	Other	235			329
	Total	$	1,439		$	3,918
Schedule of common shares that were excluded from diluted net loss per share	the following potential common shares were excluded because including them would have been anti-dilutive:
			December 31,
			2012		2013			2014
	Preferred series A		2,914,187		—			—
	Preferred series B		7,232,092		—			—
	Common stock warrants		8,208		28,406			28,406
	Common stock options		1,617,875		2,388,394			2,759,770
			11,772,362		2,416,800			2,788,176
Schedule of revenue by product	Product information – The following table provides Product sales revenue by product:
			Year ended
			December 31,
	(Dollars in thousands)		2012		2013			2014
	iCell Cardiomyocytes		$2,610		$4,787			$3,175
	iCell Neurons		2,256		2,428			3,317
	MyCell		—		222			857
	Other		312		561			728
	Total		$5,178		$7,998			$8,077
	Collaborations, partnerships and other revenue information - The following table provides Collaborations, partnerships and other revenues by significant agreement or type:
			Year ended
			December 31,
	(Dollars in thousands)		2012			2013				2014
	CIRM/Coriell		$	—		$	182			$	3,008
	MCOW		440			533				1,144
	Collaborative cell development		728			1,857				1,287
	iCell Hepatocytes		127			808				1,796
	Prototype cells		—			381				777
	Other		109			125				603
	Total		$	1,404		$	3,886			$	8,615
Schedule of revenue by geographic region	Geographical information – The following table provides percentage of total revenues by region, based on shipping locations or, in the case of CIRM, the customer location:
			Year ended
			December 31,
			2012		2013			2014
	United States of America		66	%	56	%		67	%
	Europe		24	%	38	%		28	%
	Japan		5	%	5	%		4	%
	Other		5	%	1	%		1	%
	Total		100	%	100	%		100	%

Intangible_assets_Tables

Intangible assets (Tables)	12 Months Ended
	Dec. 31, 2014
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Schedule of Intangible Assets	Intangible assets and accumulated amortization balances at December 31, 2013 and December 31, 2014, are as follows:
	(dollars in thousands)	December 31,			December 31,
		2013			2014
	Trade name	$	13		$	13
	Licenses and patents	4,578			4,722
	Non-competition agreements	641			761
		5,232			5,496
	Less accumulated amortization:
	Trade name	(13		)	(13		)
	Licenses and patents	(746		)	(1,152		)
	Non-competition agreements	(351		)	(518		)
		(1,110		)	(1,683		)
	Total, net	$	4,122		$	3,813
	As of December 31, 2013 and 2014, the trade name was fully amortized. The remaining weighted-average useful lives of the other intangible assets as of December 31, 2014 are as follows:
	Licenses and patents	11.8 years
	Non-competition agreements	5.2 years
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	The future amortization of intangible assets recorded as of December 31, 2014 is as follows:
	(Dollars in thousands)
	Years ending December 31,	Amount
	2015	$	564
	2016	428
	2017	385
	2018	333
	2019	330
	Thereafter	1,773
		$	3,813

Longterm_debt_Tables

Long-term debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Long-term Debt	Long-term debt at December 31, 2013 and 2014, consists of the following:
	(Dollars in thousands)	December 31,			December 31,
		2013			2014
	Term loan credit agreement, net of debt discount	$	11,879		$	12,131
	License agreements	18			—
		11,897			12,131
	Less current portion	(18		)	(4,541		)
	Total	$	11,879		$	7,590

Stock_options_and_restricted_c1

Stock options and restricted common stock (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	Assumptions used to value the most recent option grants were as follows:
		2012		2013		2014
	Estimated expected term	6 years		6 to 8 years		1 to 8 years
	Risk-free interest rate	0.98	%	1.70% to 2.22%		0.18% to 2.38%
	Expected volatility assumption	66	%	64% to 68%		43% to 66%
	Forfeiture rate	0% to 7%		0% to 7%		0% to 6%
	Dividend yield assumption	—	%	—	%	—	%
Number of Shares Available for Grant	The number of shares available for grant under the Company's Equity Incentive Plans, as amended (the "Plans") were as follows:
		2008 Plan		2013 Plan		Total
	Available for grant — January 1, 2012	243,665		—		243,665
	Plan amendment	262,256		—		262,256
	Grants	(99,187	)	—		(99,187	)
	Forfeitures	6,954		—		6,954
	Available for grant — December 31, 2012	413,688		—		413,688
	Plan adjustments and amendments	(421,371	)	831,659		410,288
	Grants	—		(812,116	)	(812,116	)
	Forfeitures	7,683		10,327		18,010
	Available for grant — December 31, 2013	—		29,870		29,870
	Plan adjustments and amendments	(84,494	)	630,309		545,815
	Grants	—		(599,311	)	(599,311	)
	Forfeitures	84,494		87,158		171,652
	Available for grant — December 31, 2014	—		148,026		148,026
Summary of Option Activity	A summary of option activity under the Plans as of December 31, 2014 and changes during the period then ended were as follows:
		Options		Weighted-			Weighted-
				average			average
				exercise			remaining
				price			contractual
							term
	Outstanding — January 1, 2012	1,545,938		$	8.09		8.42
	Granted	99,187		12.68
	Exercised	(20,296	)	7.41
	Forfeited	(6,954	)	12.19
	Outstanding — December 31, 2012	1,617,875		8.39			7.63
	Granted	812,116		12.31
	Exercised	(23,587	)	6.55
	Forfeited	(18,010	)	11.34
	Outstanding — December 31, 2013	2,388,394		9.7			7.63
	Granted	599,311		14.54
	Exercised	(56,283	)	6.14
	Forfeited	(171,652	)	11.33
	Outstanding — December 31, 2014	2,759,770		$	10.72		7.14
	Vested as of December 31, 2014	1,641,991		$	8.86		6.14
	Vested or expected to vest as of December 31, 2014	2,746,571		$	10.71		7.13
	Exercisable as of December 31, 2014	1,779,870		$	9.16		6.23

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Deferred Tax Assets	The components of the net deferred tax asset with the approximate income tax effect of each type of carryforward, credit and temporary differences are as follows.
	(Dollars in thousands)	31-Dec-13				31-Dec-14
	Deferred tax assets
	Operating loss carryforwards	$	41,141			$	50,387
	Tax credit carryforwards	5,529				6,290
	Other temporary differences	2,327				3,599
	Tax assets before valuation allowance	48,997				60,276
	Less: valuation allowance	(48,997		)		(60,276		)
	Net deferred taxes	$	—			$	—
Schedule of Effective Tax Rate	The effective tax rate differs from the statutory tax rate due to the following:
		Year ended December 31,
		2012			2013			2014
	U.S. Federal statutory rate	35	%		35	%		35	%
	State taxes	5			5			1.3
	Research credits	—			13.3			2.5
	Stock-based compensation	(0.5	)		(0.5	)		(0.1	)
	Other	(0.2	)		(0.1	)		(0.2	)
	Valuation allowance	(39.3	)		(52.7	)		(38.5	)
		—	%		—	%		—	%

Commitments_and_contingencies_

Commitments and contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Payments for Operating Leases	Future minimum lease payments at December 31, 2014, under operating leases with initial or remaining terms in excess of one year were as follows:
	(Dollars in thousands)
	Years ending December 31,
	2015	$	942
	2016	932
	2017	841
	2018	512
	2019	16
	Thereafter	—
		$	3,243

Description_of_business_Detail

Description of business - (Details)	12 Months Ended	1 Months Ended	0 Months Ended
	Dec. 31, 2008	Jul. 31, 2008	Jun. 27, 2013
	Business	Business
Equity, Class of Treasury Stock [Line Items]
Companies acquired	2
Cellular Dynamics International, Inc. and Stem Cell Products, Inc. [Member]
Equity, Class of Treasury Stock [Line Items]
Companies acquired		2
Series A Preferred Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Reverse stock split ratio, conversion ratio			9.75
Series B Preferred Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Reverse stock split ratio, conversion ratio			9.75
Common Class B [Member]
Equity, Class of Treasury Stock [Line Items]
Reverse stock split ratio, conversion ratio			9.75

Significant_accounting_policie3

Significant accounting policies and supplemental financial information - Textual (Details) (USD $)	1 Months Ended	12 Months Ended				36 Months Ended	1 Months Ended	0 Months Ended
	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2008	Dec. 31, 2014	Jun. 30, 2012	Dec. 31, 2013	Nov. 30, 2013
					Business				Donor
Supplemental Financial Information [Line Items]
Allowance for Doubtful Accounts Receivable, Current		$0	$0			$0		$0
Companies acquired					2
Deferred revenue		3,918,000	1,439,000			3,918,000		1,439,000
Revenues		16,692,000	11,884,000	6,582,000
Deferred revenue amount		2,479,000	869,000	236,000
Product Stem Cells, Types of Cell, Number							2
Revenue Recognition, Milestone Method, Term of Agreement	1 year
Advertising Expense		212,000	220,000	110,000
US Treasury Securities [Member]
Supplemental Financial Information [Line Items]
Investment amount		24,600,000				24,600,000
Money Market Funds [Member]
Supplemental Financial Information [Line Items]
Investment amount		1,900,000				1,900,000
Sales [Member] | Geographic Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage		100.00%	100.00%	100.00%
Sales Revenue, Net [Member] | Lilly [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage			18.00%	18.00%
Sales Revenue, Net [Member] | Hoffmann-La Roche Inc. [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage		10.00%
Sales Revenue, Net [Member] | GlaxoSmithKline plc [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage				11.00%
Sales Revenue, Net [Member] | AstraZeneca [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage			15.00%
Sales Revenue, Net [Member] | CIRM [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage		15.00%
Accounts Receivable [Member] | Lilly [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage		16.00%	21.00%
Accounts Receivable [Member] | Hoffmann-La Roche Inc. [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage		15.00%	11.00%
Accounts Receivable [Member] | AstraZeneca [Member] | Customer Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage			17.00%
UNITED KINGDOM | Sales [Member] | Geographic Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage			12.00%
SWITZERLAND | Sales [Member] | Geographic Concentration Risk [Member]
Supplemental Financial Information [Line Items]
Concentration risk, percentage			11.00%
Collaborative Agreement with ELI Lilly and Company [Member]
Supplemental Financial Information [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized		225,000	100,000	25,000		350,000
Revenue Recognition, Milestone Method, Revenue Invoiced				125,000
Deferred revenue	100,000			100,000
Notice of Grant Award to Fund Human Induced Pluripotent Stem Cell Biobank [Member]
Supplemental Financial Information [Line Items]
Number of Donors									3,000
Multiple-Element Agreement with Eli Lilly and Company [Member]
Supplemental Financial Information [Line Items]
Revenue Recognition, Milestone Method, Amount of Agreement							5,000,000
AstraZeneca UK Limited [Member]
Supplemental Financial Information [Line Items]
Revenue Recognition, Milestone Method, Amount of Agreement	1,300,000
California Institute of Regenerative Medicine [Member] | Notice of Grant Award to Fund Human Induced Pluripotent Stem Cell Biobank [Member]
Supplemental Financial Information [Line Items]
Grants Receivable									16,000,000
Proceeds from (Payments for) Other Financing Activities		5,800,000
Revenues		2,700,000
Deferred revenue amount		3,100,000
Coriell [Member] | Notice of Definitive Agreement [Member] [Domain]
Supplemental Financial Information [Line Items]
Revenue Recognition, Milestone Method, Revenue Invoiced		651,000
Revenues		462,000
Revenue Recognition, Milestone Method, Amount of Agreement								$6,300,000
Minimum [Member]
Supplemental Financial Information [Line Items]
Property, plant and equipment, useful life		3 years
Minimum [Member] | Patents [Member]
Supplemental Financial Information [Line Items]
Patent, useful life		1 year
Maximum [Member]
Supplemental Financial Information [Line Items]
Property, plant and equipment, useful life		7 years
Maximum [Member] | Patents [Member]
Supplemental Financial Information [Line Items]
Patent, useful life		20 years

Significant_accounting_policie4

Significant accounting policies and supplemental financial information - Inventories (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Raw materials	$1,598	$1,658
Work in process	436	547
Finished goods	2,422	1,679
Total	$4,456	$3,884

Significant_accounting_policie5

Significant accounting policies and supplemental financial information - Property Plant and Equipment (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Leasehold improvements	$835	$451
Production and lab equipment	7,274	4,815
Office and computer equipment	1,354	546
Construction-in-progress	162	932
Property, Plant and Equipment, Gross	9,625	6,744
Less accumulated depreciation and amortization	-5,793	-4,692
Total	$3,832	$2,052

Significant_accounting_policie6

Significant accounting policies and supplemental financial information - Accrued Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Accrued payroll, vacation and employee-related expenses	$1,173	$1,024
Accrued incentive compensation	612	1,229
Accrued royalties	721	584
Accrued incentives for sales staff	224	202
Other	420	322
Total	$3,150	$3,361

Significant_accounting_policie7

Significant accounting policies and supplemental financial information - Deferred Revenue (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	$3,918,000	$1,439,000
CIRM [Member]
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	3,142,000	924,000
Coriell [Member]
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	189,000	0
Lilly [Member]
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	258,000	280,000
Other Customer [Member]
Deferred Revenue Arrangement [Line Items]
Deferred Revenue	$329,000	$235,000

Significant_accounting_policie8

Significant accounting policies and supplemental financial information - Earnings Per Share (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the computation of net loss per share	2,788,176	2,416,800	11,772,362
Series A Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the computation of net loss per share	0	0	2,914,187
Series B Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the computation of net loss per share	0	0	7,232,092
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the computation of net loss per share	28,406	28,406	8,208
Equity Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the computation of net loss per share	2,759,770	2,388,394	1,617,875

Significant_accounting_policie9

Significant accounting policies and supplemental financial information - Product and Geographical Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$16,692,000	$11,884,000	$6,582,000
Collaborations, partnerships and other revenues	8,615,000	3,886,000	1,404,000
iCell Cardiomyocytes [Member]
Segment Reporting Information [Line Items]
Revenues	3,175,000	4,787,000	2,610,000
iCell Neurons [Member]
Segment Reporting Information [Line Items]
Revenues	3,317,000	2,428,000	2,256,000
MyCell [Member]
Segment Reporting Information [Line Items]
Revenues	857,000	222,000	0
Other [Member]
Segment Reporting Information [Line Items]
Revenues	728,000	561,000	312,000
Total [Domain]
Segment Reporting Information [Line Items]
Revenues	8,077,000	7,998,000	5,178,000
Geographic Concentration Risk [Member] | Sales [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%
Geographic Concentration Risk [Member] | Sales [Member] | UNITED STATES
Segment Reporting Information [Line Items]
Concentration risk, percentage	67.00%	56.00%	66.00%
Geographic Concentration Risk [Member] | Sales [Member] | Europe [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	28.00%	38.00%	24.00%
Geographic Concentration Risk [Member] | Sales [Member] | JAPAN
Segment Reporting Information [Line Items]
Concentration risk, percentage	4.00%	5.00%	5.00%
Geographic Concentration Risk [Member] | Sales [Member] | Countries Other than US, Japan, and Europe [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	1.00%	1.00%	5.00%
CIRM/Coriell [Member]
Segment Reporting Information [Line Items]
Collaborations, partnerships and other revenues	3,008,000	182,000	0
Medical College of Wisconsin [Member]
Segment Reporting Information [Line Items]
Collaborations, partnerships and other revenues	1,144,000	533,000	440,000
Lilly research components [Member]
Segment Reporting Information [Line Items]
Collaborations, partnerships and other revenues	1,287,000	1,857,000	728,000
iCell Hepatocytes [Member]
Segment Reporting Information [Line Items]
Collaborations, partnerships and other revenues	1,796,000	808,000	127,000
Prototype Cells [Member]
Segment Reporting Information [Line Items]
Collaborations, partnerships and other revenues	777,000	381,000	0
Other Services [Member]
Segment Reporting Information [Line Items]
Collaborations, partnerships and other revenues	$603,000	$125,000	$109,000
Medical College of Wisconsin [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration risk, percentage	13.00%

Intangible_assets_Textual_Deta

Intangible assets - Textual (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Amortization of Intangible Assets		$584,000	$522,000	$347,000
Increase in intangible due to non-compete agreement	$120,000		$70,000

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$5,496	$5,232
Finite-Lived Intangible Assets, Accumulated Amortization	-1,683	-1,110
Total, net	3,813	4,122
Trade name
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	13	13
Finite-Lived Intangible Assets, Accumulated Amortization	-13	-13
Licenses and patents
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	4,722	4,578
Finite-Lived Intangible Assets, Accumulated Amortization	-1,152	-746
Weighted average useful life of intangible assets	11 years 10 months 2 days
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	761	641
Finite-Lived Intangible Assets, Accumulated Amortization	($518)	($351)
Weighted average useful life of intangible assets	5 years 2 months 6 days

Intangible_assets_Expected_Amo

Intangible assets Expected Amortization (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
2015	$564
2016	428
2017	385
2018	333
2019	330
Thereafter	1,773
Total, net	$3,813	$4,122

Longterm_debt_Summary_of_Curre

Long-term debt - Summary of Current and Noncurrent Debt (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Long-term Debt	$12,131	$11,897
Less current portion	-4,541	-18
Total	7,590	11,879
Term loan credit agreement, net of debt discount
Debt Instrument [Line Items]
Long-term Debt	12,131	11,879
Licensing Agreements [Member]
Debt Instrument [Line Items]
Long-term Debt	$0	$18

Longterm_debt_Textual_Details

Long-term debt - Textual (Details) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Jun. 30, 2013	Jun. 28, 2013	Jun. 27, 2013
Other Income [Member]
Debt Instrument [Line Items]
Gain (Loss) from Initial Public Offering after Revaluation of Exercise Price	$20,000
Line of Credit [Member]
Debt Instrument [Line Items]
Amount borrowed under term loan credit agreement			12,000,000
Term of the credit agreement (in years)		4 years
Variable rate, reference rate on the credit agreement, percentage		6.50%
Variable rate, minimum basis spread on the reference rate, percentage		2.00%
Number of monthly installments under the credit agreement		30 months
Credit agreement, terms, exit fee on the total amount borrowed, percentage		5.00%
Credit agreement, terms, facility fee due upon execution of the agreement, percentage		0.50%
Credit agreement, terms, quarterly administrative fee, amount		2,500
Credit agreement, terms, prepayment premium minimum percentage		1.00%
Credit agreement, terms, prepayment premium maximum percentage		2.00%
Warrants issued in relation to the credit agreement, tranche 1		28,406
Term of warrants issued in relation to credit agreement (in years)		10 years
Fair value of the warrants	$261,000
Line of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Warrant, Anticipated Price of Warrant				12.68
Line of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Warrant, Anticipated Price of Warrant				12
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Variable rate, maximum basis spread on the reference rate, interest rate index, period		1 month

Shareholders_equity_Details

Shareholders' equity (Details) (USD $)	0 Months Ended
	Jul. 30, 2013	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Issuance of Stock (in shares)	3,846,000
Share price of IPO (in dollars per share)	$12
Gross proceeds form IPO	$46,200,000
Net proceeds from IPO	40,800,000
Debt Instrument, Convertible, Conversion Ratio	1
IPO triggered automatic exercise of warrants, number of warrants	$8,208
Automatic exercise of warrants, strike price of each warrant (in dollars per warrant)	$0.10
Common Stock Authorized (in shares)		100,000,000	100,000,000
Authorized Preferred Stock (in shares)		10,000,000	10,000,000
Preferred Stock, Shares Issued		0	0

Stock_options_and_restricted_c2

Stock options and restricted common stock - Assumptions used to value the most recent option grants (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated expected term			6 years
Risk free interest Rate			0.98%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum	43.00%	66.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum			66.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum	66.00%	68.00%
Dividend yield assumption	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated expected term	1 year	6 years
Risk free interest Rate	0.18%	1.70%
Forfeiture rate	0.00%	0.00%	0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated expected term	8 years	8 years
Risk free interest Rate	2.38%	2.22%
Forfeiture rate	6.00%	7.00%	7.00%

Stock_options_and_restricted_c3

Stock options and restricted common stock - Number of shares available grant (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Available for Grant [Roll Forward]
Grants	-599,311	-812,116	-99,187
Forfeitures	171,652	18,010	6,954
2008 and 2013 Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Available for Grant [Roll Forward]
Available for grant — Beginning	29,870	413,688	243,665
Plan amendment			262,256
Plan adjustments and amendments	545,815	410,288
Grants	-599,311	-812,116	-99,187
Forfeitures	171,652	18,010	6,954
Available for grant — Ending	148,026	29,870	413,688
2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Available for Grant [Roll Forward]
Available for grant — Beginning	0	413,688	243,665
Plan amendment			262,256
Plan adjustments and amendments	-84,494	-421,371
Grants	0	0	-99,187
Forfeitures	84,494	7,683	6,954
Available for grant — Ending	0	0	413,688
2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Available for Grant [Roll Forward]
Available for grant — Beginning	29,870	0	0
Plan amendment			0
Plan adjustments and amendments	630,309	831,659
Grants	-599,311	-812,116	0
Forfeitures	87,158	10,327	0
Available for grant — Ending	148,026	29,870	0

Stock_options_and_restricted_c4

Stock options and restricted common stock - Stock Option Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options Outstanding - Beginning Balance (in shares)	2,388,394	1,617,875	1,545,938
Options Granted (in shares)	599,311	812,116	99,187
Options Exercised (in shares)	-56,283	-23,587	-20,296
Options Forfeited (in shares)	-171,652	-18,010	-6,954
Options Outstanding - Ending Balance (in shares)	2,759,770	2,388,394	1,617,875	1,545,938
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options Outstanding - Beginning Balance - Weighted average exercise price (in dollars per share)	$0	$8.39	$8.09
Options Granted - Weighted average exercise price (in dollars per share)	$14.54	$12.31	$12.68
Options Exercised - Weighted average exercise price (in dollars per share)	$6.14	$6.55	$7.41
Options Forfeited - Weighted average exercise price (in dollars per share)	$11.33	$11.34	$12.19
Options Outstanding - Ending Balance - Weighted average exercise price (in dollars per share)	$10.72	$0	$8.39	$8.09
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options Outstanding - Weighted average remaining contractual term	7 years 1 month 20 days	7 years 7 months 16 days	7 years 7 months 16 days	8 years 5 months 2 days
Options Vested (in shares)	1,641,991
Options Vested or expected to vest (in shares)	2,746,571
Options Exercisable (in shares)	1,779,870
Options Vested - Weighted Average Grant Date Fair Value (in dollars per share)	$8.86
Options Vested or expected to vest - Weighted Average Exercise Price (in dollars per share)	$10.71
Options Exercisable - Weighted Average Exercise Price (in dollars per share)	$9.16
Options Vested - Weighted Average Remaining Contractual Term	6 years 1 month 20 days
Options Vested or expected to vest - Weighted Average Remaining Contractual Term	7 years 1 month 17 days
Options Exercisable - Average Remaining Contractual Term	6 years 2 months 22 days

Stock_options_and_restricted_c5

Stock options and restricted common stock - Textual (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Contractual Term	10 years
Weighted-average grant-date fair value of stock options granted	$9.65	$8.31	$4.10
Aggregate intrinsic value of outstanding stock options	$70,000
Compensation costs not yet recognized related to nonvested awards	$7,100,000
Compensation costs not yet recognized related to nonvested awards, period for recognition	2 years 9 months 8 days

Income_Taxes_Textual_Details

Income Taxes - Textual (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$130
Tax credit carryforward	3.3
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	97
Tax credit carryforward	$4.50

Income_Taxes_Deferred_Tax_Asse

Income Taxes - Deferred Tax Assets and Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets
Operating loss carryforwards	$50,387	$41,141
Tax credit carryforwards	6,290	5,529
Other temporary differences	3,599	2,327
Tax assets before valuation allowance	60,276	48,997
Less: valuation allowance	-60,276	-48,997
Net deferred taxes	$0	$0

Income_Taxes_Rate_Reconciliati

Income Taxes - Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%
State taxes	1.30%	5.00%	5.00%
Research credits	2.50%	13.30%	0.00%
Stock-based compensation	-0.10%	-0.50%	-0.50%
Other	-0.20%	-0.10%	-0.20%
Valuation allowance	-38.50%	-52.70%	-39.30%
Effective Income Tax Rate	0.00%	0.00%	0.00%

401k_savings_plan_Details

401(k) savings plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Contributions to 401(k)	$63,000	$53,000	$48,000

Commitments_and_contingencies_1

Commitments and contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Operating leases, rent expense	$949,000	$823,000	$577,000
2015	942,000
2016	932,000
2017	841,000
2018	512,000
2019	16,000
Thereafter	0
Total	$3,243,000

Relatedparty_transactions_Deta

Related-party transactions (Details) (Consulting Agreement [Member], USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2012
Related Party Transaction [Line Items]
Related party consulting agreement, general and administrative expense	$302,000
Scientific Advisor [Member]
Related Party Transaction [Line Items]
Related party consulting agreement, general and administrative expense		$302,000	$302,000