Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 12,177	$ 21,679
Marketable securities	45,088	41,868
Interest receivable	258	190
Accounts receivable	3,667	4,129
Other current assets	120	203
Prepaid expenses	236	296
Total current assets	61,546	68,365
Marketable securities, non-current	12,795	12,584
Property and equipment, net	1,464	1,543
Other assets	39	41
Total assets	75,844	82,533
Current liabilities:
Accounts payable and accrued liabilities	2,533	4,013
Accrued compensation and employee benefits	1,134	2,473
Deferred revenues	2,286	2,304
Total current liabilities	5,953	8,790
Deferred revenues, non-current	8,305	8,847
Total liabilities	14,258	17,637
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value; 80,000,000 shares authorized, 53,546,316 and 53,058,525 shares issued and outstanding at March 31, 2013 and December 31, 2012, respectively	535	531
Additional paid-in capital	343,420	339,848
Accumulated deficit	(282,394)	(275,509)
Accumulated other comprehensive income	25	26
Total stockholders' equity	61,586	64,896
Total liabilities and stockholders' equity	$ 75,844	$ 82,533