CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Total
Balances at Dec. 31, 2008	$ 5	$ 217,647	$ (2,541)	$ (109,665)	$ 105,446
Balances (in shares) at Dec. 31, 2008	46,141,743
Components of comprehensive loss:
Net loss	0	0		(14,577)	(14,577)
Unrealized gain/loss on investments	0	0	1,518	0	1,518
Foreign currency translation adjustment	0	0	(210)	0	(210)
Comprehensive loss					(13,269)
Stock-based compensation expense	0	3,690	0	0	3,690
Issuance of common stock upon exercise of stock options for cash	0	358	0	0	358
Issuance of common stock upon exercise of stock options for cash (in shares)	244,770
Issuance of common stock under employee stock purchase plan	0	127	0	0	127
Issuance of common stock under employee stock purchase plan (in shares)	74,041
Balances at Dec. 31, 2009	5	221,822	(1,233)	(124,242)	96,352
Balances (in shares) at Dec. 31, 2009	46,460,554
Components of comprehensive loss:
Net loss	0	0		(18,067)	(18,067)
Unrealized gain/loss on investments	0	0	(66)	0	(66)
Foreign currency translation adjustment	0	0	(32)	0	(32)
Comprehensive loss					(18,165)
Stock-based compensation expense	0	3,331	0	0	3,331
Issuance of common stock upon exercise of stock options for cash	0	4,539	0	0	4,539
Issuance of common stock upon exercise of stock options for cash (in shares)	1,681,591
Issuance of common stock under employee stock purchase plan	0	127	0	0	127
Issuance of common stock under employee stock purchase plan (in shares)	74,041
Balances at Dec. 31, 2010	5	229,692	(1,331)	(142,309)	86,057
Balances (in shares) at Dec. 31, 2010	48,142,145				48,142,145
Components of comprehensive loss:
Net loss	0	0		(18,640)	(18,640)
Unrealized gain/loss on investments	0	0	(185)	0	(185)
Foreign currency translation adjustment	0	0	(182)	0	(182)
Comprehensive loss					(19,007)
Stock-based compensation expense	0	3,769	0	0	3,769
Issuance of common stock upon exercise of stock options for cash	0	450	0	0	450
Issuance of common stock upon exercise of stock options for cash (in shares)	190,480
Issuance of common stock under employee stock purchase plan	0	66	0	0	66
Issuance of common stock under employee stock purchase plan (in shares)	35,851
Balances at Dec. 31, 2011	$ 5	$ 233,977	$ (1,698)	$ (160,949)	$ 71,335
Balances (in shares) at Dec. 31, 2011	48,368,476				48,368,476