Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 164,269	$ 347,845
Marketable securities	353,680	125,710
Prepaid expenses and other current assets	6,016	6,434
Total current assets	523,965	479,989
Marketable securities	347,814	18,448
Property and equipment, net	82,614	15,740
Intangible assets, net	24,456	28,219
Goodwill	13,128	13,128
Restricted cash and other non-current assets	10,360	1,215
Total assets	1,002,337	556,739
Current liabilities:
Accounts payable	6,334	2,954
Accrued expenses and other current liabilities	28,145	14,649
Deferred revenue, current portion	5,889	25,375
Total current liabilities	40,368	42,978
Deferred rent, net of current portion	8,294	8,674
Deferred revenue, net of current portion	35,959	5,302
Contingent consideration, net of current portion	5,082	6,321
Construction financing lease obligation	61,901
Other non-current liabilities	237	2,207
Total liabilities	$ 151,841	$ 65,482
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at December 31, 2015 and December 31, 2014
Common stock, $0.01 par value, 125,000 shares authorized; 36,894 and 32,340 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	$ 369	$ 323
Additional paid-in capital	1,166,585	638,389
Accumulated other comprehensive loss	(2,291)	(71)
Accumulated deficit	(314,167)	(147,384)
Total stockholders' equity	850,496	491,257
Total liabilities and stockholders' equity	$ 1,002,337	$ 556,739