CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 271,807	$ 61,349
Marketable securities	105,359	130,180
Accounts receivable	33,727	7,427
Unbilled revenue	2,400	2,909
Prepaid expenses and other current assets	2,531	3,465
Total current assets	415,824	205,330
Property and equipment, net	22,819	25,422
Restricted cash	20,719	20,719
Intangible assets, net	4,059	4,589
Other long-term assets	156	156
Total assets	463,577	256,216
Current liabilities:
Accounts payable	1,895	7,433
Accrued expenses	17,345	10,348
Deferred revenue	9,770	5,490
Other current liabilities	579	518
Total current liabilities	29,589	23,789
Deferred revenue, net of current portion	17,098	25,508
Other long-term liabilities	250	551
Total liabilities	$ 46,937	$ 49,848
Commitments and contingencies (Note 9)
Stockholders' Equity:
Preferred stock, $0.01 par value per share; 5,000 shares authorized at June 30, 2015 and December 31, 2014, 100 shares of Series A Junior Participating Preferred Stock, $0.01 par value per share designated and no shares issued and outstanding
Common stock, $0.0001 par value per share; 100,000 shares authorized at June 30, 2015 and December 31, 2014, 68,844 shares issued and 68,725 shares outstanding at June 30, 2015 and 54,486 shares issued and outstanding at and December 31, 2014	$ 7	$ 5
Additional paid-in capital	811,819	575,438
Accumulated other comprehensive income (loss)	20	(16)
Accumulated deficit	(393,158)	(369,059)
Treasury stock, at cost, 119 shares and zero shares at June 30, 2015 and December 31, 2014, respectively	(2,048)
Total stockholders' equity	416,640	206,368
Total liabilities and stockholders' equity	$ 463,577	$ 256,216