CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 97,711	$ 70,154
Marketable securities	2,484	21,980
Restricted cash	6,628	10,847
Prepaid expenses and other current assets	16,571	16,295
Total current assets	123,394	119,276
Restricted cash	1,860	958
Property and equipment, net	26,972	28,426
Intangible assets, net	6,114	6,541
Goodwill	51,245	51,967
Other non-current assets	11,734	810
Total assets	221,319	207,978
Current liabilities:
Accounts payable	6,150	9,301
Accrued expenses	13,881	19,550
Accrued interest	2,031	5,078
Deferred revenue	5,943	10,010
Other current liabilities	3,491	1,600
Total current liabilities	31,496	45,539
Deferred revenue	3,399	2,500
Convertible notes payable	319,543	319,187
Other non-current liabilities	17,464	8,687
Total liabilities	371,902	375,913
Commitments and contingencies
Stockholders' deficit:
Preferred stock, $0.01 par value, 2,000,000 shares authorized; no shares issued and outstanding as of March 31, 2019 and December 31, 2018, respectively	0	0
Common stock, $0.01 par value, 600,000,000 shares authorized at March 31, 2019 and December 31, 2018; 469,909,313 shares issued and 469,453,883 shares outstanding at March 31, 2019 and 384,906,037 shares issued and 384,450,607 shares outstanding at December 31, 2018	4,699	3,849
Additional paid-in capital	1,201,853	1,140,964
Accumulated deficit	(1,342,325)	(1,299,107)
Treasury stock, 455,430 shares, cost basis at both March 31, 2019 and December 31, 2018	(2,450)	(2,450)
Accumulated other comprehensive loss	(12,360)	(11,191)
Total stockholders' deficit	(150,583)	(167,935)
Total liabilities and stockholders' deficit	$ 221,319	$ 207,978