CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 144,353	$ 93,108
Marketable securities	91,126	137,548
Restricted cash	30,314	34,964
Accounts receivable	233	2,320
Prepaid expenses and other current assets	21,804	19,317
Total current assets	287,830	287,257
Restricted cash	4,590	2,422
Property and equipment, net	40,184	32,342
Intangible assets, net	9,225	10,793
Goodwill	51,673	53,065
Other non-current assets	799	159
Total assets	394,301	386,038
Current liabilities:
Accounts payable	5,685	11,889
Accrued expenses	24,508	26,734
Accrued interest	5,078	0
Deferred revenue	30,079	34,469
Notes payable	0	395
Other current liabilities	1,056	3,007
Total current liabilities	66,406	76,494
Deferred revenue	2,500	4,171
Convertible notes payable	316,339	0
Other non-current liabilities	14,602	12,704
Total liabilities	399,847	93,369
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred stock, $0.01 par value, 2,000,000 shares authorized; no shares issued and outstanding at December 31, 2016 and 2015	0	0
Common stock, $0.01 par value, 600,000,000 shares authorized at December 31, 2016 and 2015; and 271,701,397 shares issued and 271,245,967 shares outstanding at December 31, 2016 and 270,426,662 shares issued and 269,971,232 shares outstanding at December 31, 2015	2,717	2,704
Additional paid-in capital	935,997	951,569
Accumulated deficit	(929,996)	(650,030)
Treasury stock, 455,430 shares, cost basis at both December 31, 2016 and 2015	(2,450)	(2,450)
Accumulated other comprehensive loss	(11,814)	(9,124)
Total stockholders’ equity (deficit)	(5,546)	292,669
Total liabilities and stockholders’ equity (deficit)	$ 394,301	$ 386,038