Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 20,471	$ 38,837
Marketable securities, available-for-sale	23,499	11,541
Restricted cash	3,182	3,119
Receivables and other assets	4,178	4,590
Total current assets	51,330	58,087
Long-term investments	1,971	1,980
Property and equipment, net	2,639	3,935
Intangible assets, net	1,660	1,972
Other assets	379	379
Total assets	57,979	66,353
Current liabilities:
Accounts payable and accrued expenses	5,201	3,503
Deferred revenue	0	150
Total current liabilities	5,201	3,653
Long-term liabilities:
Deferred rent	856	1,288
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, 160,000 shares authorized, 90,334 and 86,778 shares issued and outstanding at December 31, 2014 and 2013, respectively	903	868
Additional paid-in capital	446,698	439,708
Accumulated deficit	(395,667)	(379,175)
Accumulated other comprehensive (loss) income	(12)	11
Total stockholders' equity	51,922	61,412
Total liabilities and stockholders' equity	$ 57,979	$ 66,353