CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 62,267	$ 196,172
Marketable securities	203,357	142,877
Accounts receivable	78,375	1,224
Prepaid expenses	3,782	1,806
Other current assets	663	305
Total current assets	348,444	342,384
Property and equipment, net	18,294	14,841
Other assets	2,112	2,044
Total assets	368,850	359,269
Current liabilities:
Accounts payable	1,150	2,967
Accrued expenses	12,342	11,708
Deferred revenue	4,578	5,866
Lease exit liability	1,459	2,020
Other liabilities	0	727
Total current liabilities	19,529	23,288
Deferred revenue, net of current portion	10,740	12,631
Lease exit liability, net of current portion	1,120	2,693
Deferred rent liability	6,758	7,320
Other Liabilities, Noncurrent	727	0
Total liabilities	38,874	45,932
Stockholders' equity:
Common stock, $0.01 par value - 125,000,000 shares authorized, 34,694,039 and 34,345,754 shares outstanding at June 30, 2016 and December 31, 2015, respectively	347	343
Additional paid-in capital	553,655	547,185
Accumulated deficit	(224,085)	(234,186)
Accumulated other comprehensive loss	59	(5)
Total stockholders' equity	329,976	313,337
Total liabilities and stockholders' equity	$ 368,850	$ 359,269