Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 237,962	$ 278,887
Marketable securities	490,812	425,491
Tenant improvements receivable	2,712	8,542
Prepaid expenses	13,893	8,209
Other current assets and receivables	13,328	3,085
Total current assets	758,707	724,214
Marketable securities	413,856	180,452
Property and equipment, net	182,358	156,955
Intangible assets, net	17,872	20,694
Goodwill	13,128	13,128
Restricted cash and other non-current assets	19,835	22,679
Total assets	1,405,756	1,118,122
Current liabilities:
Accounts payable	12,309	13,664
Accrued expenses and other current liabilities	42,595	54,660
Deferred revenue, current portion	21,897	6,209
Total current liabilities	76,801	74,533
Deferred rent, net of current portion	2,761	10,408
Deferred revenue, net of current portion	27,600	40,204
Contingent consideration, net of current portion	2,961	3,277
Financing lease obligation, net of current portion	154,240	120,140
Other non-current liabilities	75	120
Total liabilities	264,438	248,682
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at September 30, 2017 and December 31, 2016
Common stock, $0.01 par value, 125,000 shares authorized; 45,785 and 40,691 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	458	407
Additional paid-in capital	1,939,537	1,447,856
Accumulated other comprehensive loss	(2,097)	(1,149)
Accumulated deficit	(796,580)	(577,674)
Total stockholders’ equity	1,141,318	869,440
Total liabilities and stockholders’ equity	$ 1,405,756	$ 1,118,122