Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 59,406	$ 49,826
Marketable securities	480,040	193,482
Interest receivable	562	240
Accounts receivable	4,977	3,343
Prepaid expenses and other current assets	5,064	1,506
Total current assets	550,049	248,397
Marketable securities, non-current	34,182	1,012
Property and equipment, net	37,223	31,066
Goodwill	1,585	1,585
Restricted cash and other non-current assets	4,688	4,681
Total assets	627,727	286,741
Current liabilities:
Accounts payable and accrued liabilities	14,388	11,035
Accrued compensation and employee benefits	4,346	5,479
Deferred revenues	57,215	28,345
Total current liabilities	75,949	44,859
Deferred revenues, non-current	137,731	29,244
Build-to-suit lease obligation	26,180	24,738
Total liabilities	239,860	98,841
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value; 160,000,000 shares authorized, 101,623,521 and 85,598,534 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	1,016	856
Additional paid-in capital	918,197	682,809
Accumulated deficit	(531,189)	(495,479)
Accumulated other comprehensive loss	(157)	(286)
Total stockholders' equity	387,867	187,900
Total liabilities and stockholders' equity	$ 627,727	$ 286,741