Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 61,291	$ 20,250
Certificates of deposit	249	1,494
Prepaid expenses	773	907
State research and development credit receivable	329	542
Other receivables	1,328	196
Total current assets	63,970	23,389
Leasehold improvements and equipment:
Leasehold improvements	5,588	5,085
Computer equipment	1,133	636
Lab equipment	3,724	3,297
Total leasehold improvements and equipment	10,445	9,018
Less accumulated depreciation and amortization	(3,858)	(2,978)
Leasehold improvements and equipment, net	6,587	6,040
Total assets	70,557	29,429
Current liabilities:
Accounts payable	612	972
Accrued expenses	2,861	1,659
Income taxes payable	130	0
Current portion of deferred rent	84	84
Obligations under capital leases	35	55
Current portion of long term debt	154	149
Total current liabilities	3,876	2,919
Long term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Obligations under capital leases	46	38
Deferred rent, excluding current portion	1,321	1,405
Total long-term liabilities	8,354	8,583
Total liabilities	12,230	11,502
Stockholders' Equity
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at December 31, 2013 and 2012; issued and outstanding shares — 0 at December 31, 2013 and 2012	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at December 31, 2013 and 38,833,334 at December 31, 2012; issued and outstanding shares — 26,573,023 at December 31, 2013, and 20,985,192 at December 31, 2012	266	210
Additional paid-in capital	194,038	122,514
Deficit accumulated during the development stage	(135,977)	(104,797)
Total stockholders' equity	58,327	17,927
Total liabilities and stockholders' equity	70,557	29,429
Iowa State University Research Park [Member]
Long term liabilities:
Notes Payable, Noncurrent	687	840
City of Ames [Member]
Long term liabilities:
Notes Payable, Noncurrent	$ 300	$ 300