Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 24,841	$ 5,069
Marketable securities, available-for-sale	35,658	30,552
Restricted cash	192	3,311
Deferred contract costs	10,502	5,513
Receivables and other assets	5,124	3,422
Total current assets	76,317	47,867
Long-term investments	2,209	2,046
Property and equipment, net	606	1,173
Intangible assets, net	703	810
Other assets	659	388
Total assets	80,494	52,284
Current liabilities:
Accounts payable and accrued expenses	5,217	4,127
Deferred revenue	11,700	3,018
Total current liabilities	16,917	7,145
Long-term liabilities:
Commitments and contingencies (Notes 6 and 7)
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized, none issued and outstanding	0	0
Common stock, $0.01 par value, 50,000 shares authorized, 21,802 and 11,052 shares issued and outstanding at December 31, 2017 and 2016, respectively	218	111
Additional paid-in capital	489,975	458,881
Accumulated deficit	(426,738)	(413,878)
Accumulated other comprehensive income	122	25
Total stockholders’ equity	63,577	45,139
Total liabilities and stockholders’ equity	$ 80,494	$ 52,284