Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 40,660	$ 32,533
Short-term marketable securities	52,894	62,410
Accounts receivable (net of allowance for doubtful accounts; 2016—$4,113, 2015—$3,988)	33,611	37,164
Prepaid expenses and other current assets	11,852	10,843
Total current assets	139,017	142,950
Property and equipment, net	39,052	39,746
Other assets	2,020	1,921
Total assets	180,089	184,617
Current liabilities:
Accounts payable	4,796	8,585
Accrued compensation and employee benefits	20,514	22,239
Accrued license fees	2,334	2,287
Accrued expenses and other current liabilities	11,140	8,922
Deferred revenues	235	431
Other current liabilities	208	208
Total current liabilities	39,227	42,672
Other liabilities	2,306	2,410
Commitments and contingencies
Stockholders' equity:
Common stock	3	3
Additional paid- in capital	408,516	395,059
Accumulated other comprehensive income	767	2,752
Accumulated deficit	(240,620)	(228,169)
Treasury stock, at cost	(30,110)	(30,110)
Total stockholders' equity	138,556	139,535
Total liabilities and stockholders' equity	$ 180,089	$ 184,617