Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 43,159	$ 38,696
Marketable securities, available-for-sale	37,639	8,733
Restricted cash	3,059	2,998
Receivables and other assets	2,152	3,130
Total current assets	86,009	53,557
Long-term investments	2,225	5,928
Property and equipment, net	5,284	6,226
Intangible assets, net	2,813	2,871
Other assets	191	191
Total assets	96,522	68,773
Current liabilities:
Accounts payable and accrued expenses	5,629	6,362
Deferred revenue	150	99
Total current liabilities	5,779	6,461
Long-term liabilities:
Deferred rent	1,657	1,964
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, 86,136 and 71,913 shares issued and outstanding at December'31, 2012 and 2011, respectively	861	719
Additional paid-in capital	435,915	384,087
Accumulated deficit	(347,937)	(325,038)
Accumulated other comprehensive income	247	580
Total stockholders' equity	89,086	60,348
Total liabilities and stockholders' equity	$ 96,522	$ 68,773