Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 203,377	$ 190,404
Certificates of deposit	4,202	12,393
Prepaid expenses	11,344	8,333
Income tax receivable	2,519	15,604
State research and development credit receivable	440	13
Other receivables	12,570	3,716
Total current assets	234,452	230,463
Leasehold improvements and equipment:
Leasehold improvements	6,139	6,022
Computer equipment	2,220	1,399
Lab equipment	4,954	4,110
Contract manufacturing organization equipment	1,067	1,023
Total leasehold improvements and equipment	14,380	12,554
Less accumulated depreciation and amortization	(5,582)	(4,955)
Leasehold improvements and equipment, net	8,798	7,599
Total assets	243,250	238,062
Current liabilities:
Accounts payable	1,474	2,412
Accrued expenses	5,954	9,367
Current portion of unearned revenue	936	12,966
Current portion of deferred rent	85	84
Current portion of obligations under capital leases	31	35
Current portion of notes payable	556	157
Total current liabilities	9,036	25,021
Long-term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable and obligations under capital leases	450	941
Unearned revenue	809	1,085
Deferred rent	1,196	1,238
Total long-term liabilities	8,455	9,264
Total liabilities	17,491	34,285
Stockholders' Equity:
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at June 30, 2015 and December 31, 2014; issued and outstanding shares — 0 at June 30, 2015 and December 31, 2014	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at June 30, 2015 and December 31, 2014; issued 28,679,388 and 27,991,242 at June 30, 2015 and December 31, 2014, respectively, and outstanding 28,661,588 and 27,980,849 at June 30, 2015 and December 31, 2014, respectively	287	280
Additional paid-in capital	262,055	236,838
Treasury stock, at cost: 17,800 and 10,393 shares at June 30, 2015 and December 31, 2014, respectively	(551)	(222)
Accumulated deficit	(36,032)	(33,119)
Total stockholders' equity	225,759	203,777
Total liabilities and stockholders' equity	$ 243,250	$ 238,062