Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 38,837	$ 43,159
Marketable securities, available-for-sale	11,541	37,639
Restricted cash	3,119	3,059
Receivables and other assets	4,590	2,152
Total current assets	58,087	86,009
Long-term investments	1,980	2,225
Property and equipment, net	3,935	5,284
Intangible assets, net	1,972	2,813
Other assets	379	191
Total assets	66,353	96,522
Current liabilities:
Accounts payable and accrued expenses	3,503	5,629
Deferred revenue	150	150
Total current liabilities	3,653	5,779
Long-term liabilities:
Deferred rent	1,288	1,657
Commitments and contingencies (Notes 6 and 7)
Stockholders' equity:
Preferred stock, $0.01 par value, 5,000 shares authorized, none issued and outstanding
Common stock, $0.01 par value, 160,000 shares authorized, 86,778 and 86,136 shares issued and outstanding at December 31, 2013 and 2012, respectively	868	861
Additional paid-in capital	439,708	435,915
Accumulated deficit	(379,175)	(347,937)
Accumulated other comprehensive income	11	247
Total stockholders' equity	61,412	89,086
Total liabilities and stockholders' equity	$ 66,353	$ 96,522