Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 93,501	$ 43,248
Investment debt securities, available-for-sale	665,016	392,912
Accounts receivable, net	36,360	25,694
Prepaid expenses and other current assets	24,312	20,571
Total current assets	819,189	482,425
Fixed assets, net	6,814	10,411
Inventory, net	7,686	7,108
Security deposits	8,374	9,223
Other assets	10,906
Total assets	852,969	509,167
Current liabilities:
Accounts payable, accrued expenses and other liabilities	115,562	105,109
Short-term interest payable	8,050	7,475
Short-term portion of deferred revenue	1,622	1,621
Total current liabilities	125,234	114,205
Long-term liabilities:
Long-term debt	545,009	371,250
Long-term other liabilities	7,523	3,771
Long-term portion of deferred revenue		811
Total liabilities	677,766	490,037
Commitments and contingencies (Note 15)
Stockholders' equity:
Common stock par value $0.001 per share; 45,000,000 shares authorized; 32,696,384 and 29,693,876 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	33	30
Additional paid-in capital	2,116,481	1,800,144
Accumulated other comprehensive loss, net	(836)	(2,259)
Accumulated deficit	(1,940,475)	(1,778,785)
Total stockholders' equity	175,203	19,130
Total liabilities and stockholders' equity	$ 852,969	$ 509,167