Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 160,527	$ 195,620
Certificates of deposit	0	2,180
Prepaid expenses and other current assets	4,048	4,954
Income tax receivable	4,259	0
Other receivables	3,180	5,388
Total current assets	172,014	208,142
Property and equipment, net	7,435	10,400
Total assets	179,449	218,542
Current liabilities:
Accounts payable	1,843	3,661
Accrued expenses	19,537	8,761
Income taxes payable	0	859
Current portion of unearned revenue	838	892
Current portion of deferred rent	85	96
Current portion of notes payable and obligations under capital leases	242	571
Total current liabilities	22,545	14,840
Long-term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable and obligations under capital leases	395	368
Unearned revenue	56	407
Deferred rent	1,109	1,153
Total long-term liabilities	7,560	7,928
Total liabilities	30,105	22,768
Stockholders' equity:
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at June 30, 2016 and December 31, 2015; issued and outstanding shares — 0 at June 30, 2016 and December 31, 2015	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at June 30, 2016 and December 31, 2015; issued 28,987,523 and 28,838,176 at June 30, 2016 and December 31, 2015, respectively, and outstanding 28,962,296 and 28,814,142 at June 30, 2016 and December 31, 2015, respectively	290	288
Additional paid-in capital	286,300	276,610
Treasury stock, at cost: 25,227 and 24,034 shares at June 30, 2016 and December 31, 2015, respectively	(784)	(771)
Accumulated deficit	(136,462)	(80,353)
Total stockholders' equity	149,344	195,774
Total liabilities and stockholders' equity	$ 179,449	$ 218,542