Stock-Based Compensation (Detail) - Status Of Unvested Share-based Payment Awards (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Shares underlying awards unvested at December 31, 2012	3,834,606
Shares underlying awards unvested at December 31, 2012 (in Dollars per share)	$ 1.05
Shares underlying options granted	409,500	1,953,500
Shares underlying options granted (in Dollars per share)	$ 0.58	$ 0.48
Shares underlying restricted stock units granted	338,018	199,998
Shares underlying restricted stock units granted (in Dollars per share)	$ 1.69
Shares underlying options vested	(586,064)
Shares underlying options vested (in Dollars per share)	$ 0.55
Shares underlying restricted stock units vested	(513,984)	(883,256)
Shares underlying restricted stock units vested (in Dollars per share)	$ 3.02
Shares underlying options cancelled	(67,050)
Shares underlying options cancelled (in Dollars per share)	$ 1.00
Shares underlying restricted stock units cancelled	(21,227)
Shares underlying restricted stock units cancelled (in Dollars per share)	$ 3.25
Shares underlying awards unvested at March 31, 2013	3,393,799
Shares underlying awards unvested at March 31, 2013 (in Dollars per share)	$ 0.84