Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 686,334	$ 278,887
Marketable securities	409,100	425,491
Tenant improvements receivable	4,334	8,542
Prepaid expenses	15,036	8,209
Restricted cash and other current assets	3,814	3,085
Total current assets	1,118,618	724,214
Marketable securities	101,625	180,452
Property and equipment, net	180,419	156,955
Intangible assets, net	18,812	20,694
Goodwill	13,128	13,128
Restricted cash and other non-current assets	24,528	22,679
Total assets	1,457,130	1,118,122
Current liabilities:
Accounts payable	14,424	13,664
Accrued expenses and other current liabilities	43,748	54,660
Deferred revenue, current portion	19,666	6,209
Total current liabilities	77,838	74,533
Deferred rent, net of current portion	2,937	10,408
Deferred revenue, net of current portion	19,065	40,204
Contingent consideration, net of current portion	3,219	3,277
Financing lease obligation, net of current portion	153,962	120,140
Other non-current liabilities	90	120
Total liabilities	257,111	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 June 30, 2017 and December 31, 2016
Common stock, $0.01 par value, 125,000 shares authorized; 45,539 and 40,691 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	455	407
Additional paid-in capital	1,918,754	1,447,856
Accumulated other comprehensive loss	(1,415)	(1,149)
Accumulated deficit	(717,775)	(577,674)
Total stockholders’ equity	1,200,019	869,440
Total liabilities and stockholders’ equity	$ 1,457,130	$ 1,118,122