CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 132,225	$ 93,108
Marketable securities	301,642	137,548
Restricted cash	29,619	34,964
Accounts receivable	406	2,320
Prepaid expenses and other current assets	20,703	19,317
Total current assets	484,595	287,257
Restricted cash	6,489	2,422
Property and equipment, net	36,558	32,342
Intangible assets, net	10,962	10,793
Goodwill	53,766	53,065
Other non-current assets	137	159
Total assets	592,507	386,038
Current liabilities:
Accounts payable	11,237	11,889
Accrued expenses	27,147	26,734
Accrued interest	2,099	0
Deferred revenue	28,907	34,469
Notes payable	252	395
Deferred rent	1,337	1,409
Other current liabilities	72	1,598
Total current liabilities	71,051	76,494
Deferred revenue	8,091	4,171
Convertible notes payable	315,271	0
Deferred rent	9,413	9,534
Other non-current liabilities	3,248	3,170
Total liabilities	$ 407,074	$ 93,369
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value, 2,000,000 shares authorized; no shares issued and outstanding as of March 31, 2016 and December 31, 2015, respectively	$ 0	$ 0
Common stock, $0.01 par value, 600,000,000 shares authorized at March 31, 2016 and December 31, 2015; 271,226,476 shares issued and 270,771,046 shares outstanding at March 31, 2016 and 270,426,662 shares issued and 269,971,232 shares outstanding at December 31, 2015	2,712	2,704
Additional paid-in capital	920,001	951,569
Accumulated deficit	(727,282)	(650,030)
Treasury stock, 455,430 shares, cost basis at both March 31, 2016 and December 31, 2015	(2,450)	(2,450)
Accumulated other comprehensive loss	(7,548)	(9,124)
Total stockholders’ equity	185,433	292,669
Total liabilities and stockholders’ equity	$ 592,507	$ 386,038