Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 30,550	$ 40,020
Short-term investments	116,018	87,271
Accounts receivable	1,698	51,090
Prepaid expenses and other current assets	1,532	1,449
Total current assets	149,798	179,830
Property and equipment, net	1,131	1,210
Long-term investments	30,508	7,929
Other assets	327	359
Total assets	181,764	189,328
Current liabilities:
Accounts payable	449	1,400
Accrued liabilities	7,195	8,575
Deferred revenue	68,997	22,962
Total current liabilities	76,641	32,937
Long-term debt, net	4,700	4,676
Noncurrent deferred revenue	74,554	72,197
Other non-current liabilities	337	251
Total liabilities	156,232	110,061
Commitments
Stockholders' equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.001 par value, 200,000,000 shares authorized; 49,071,361 and 48,837,060 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	49	49
Additional paid-in capital	371,749	368,553
Note receivable	(16)	(16)
Accumulated other comprehensive loss	(302)	(119)
Accumulated deficit	(345,948)	(289,200)
Total stockholders' equity	25,532	79,267
Total liabilities and stockholders' equity	$ 181,764	$ 189,328