Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 63,377	$ 43,248
Investment debt securities, available-for-sale	648,994	392,912
Accounts receivable, net	32,822	25,694
Prepaid expenses and other current assets	23,891	20,571
Total current assets	769,084	482,425
Fixed assets, net	5,973	10,411
Inventory, net	9,348	7,108
Security deposits	8,205	9,223
Other assets	9,484
Total assets	802,094	509,167
Current liabilities:
Accounts payable, accrued expenses and other liabilities	133,295	105,109
Short-term interest payable	5,463	7,475
Short-term portion of deferred revenue	1,216	1,621
Total current liabilities	139,974	114,205
Long-term liabilities:
Long-term debt	525,339	371,250
Long-term other liabilities	6,046	3,771
Long-term portion of deferred revenue		811
Total liabilities	671,359	490,037
Commitments and contingencies (Note 15)
Stockholders' equity:
Common stock par value $0.001 per share; 45,000,000 shares authorized; 32,733,447 and 29,693,876 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively	33	30
Additional paid-in capital	2,157,080	1,800,144
Accumulated other comprehensive loss, net	(1,070)	(2,259)
Accumulated deficit	(2,025,308)	(1,778,785)
Total stockholders' equity	130,735	19,130
Total liabilities and stockholders' equity	$ 802,094	$ 509,167