Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 49,826	$ 22,061
Marketable securities	193,482	120,474
Interest receivable	240	224
Accounts receivable	3,343	4,972
Prepaid expenses and other current assets	1,506	1,849
Total current assets	248,397	149,580
Marketable securities, non-current	1,012
Property and equipment, net	31,066	6,557
Goodwill	1,585	1,585
Other assets	4,681	169
Total assets	286,741	157,891
Current liabilities:
Accounts payable and accrued liabilities	11,035	6,261
Accrued compensation and employee benefits	5,479	2,885
Deferred revenues	28,345	4,145
Total current liabilities	44,859	13,291
Deferred revenues, non-current	29,244	4,460
Build-to-suit lease obligation	24,738	3,945
Total liabilities	98,841	21,696
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value; 160,000,000 shares authorized, 85,598,534 and 70,871,902 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	856	709
Additional paid-in capital	682,809	576,377
Accumulated deficit	(495,479)	(440,911)
Accumulated other comprehensive income (loss)	(286)	20
Total stockholders' equity	187,900	136,195
Total liabilities and stockholders' equity	$ 286,741	$ 157,891