Stock-Based Compensation (Detail) - Summary of Restricted Stock Units Activity (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Awards outstanding, December 31, 2012	913,027
Awards outstanding, December 31, 2012 (in Dollars per share)	$ 0
Restricted stock units granted	338,018	199,998
Restricted stock units granted (in Dollars per share)	$ 0
Restricted stock units settled by delivery of common stock upon vesting	(513,984)	(883,256)
Restricted stock units settled by delivery of common stock upon vesting (in Dollars per share)	$ 0
Restricted stock units cancelled	(21,227)
Restricted stock units cancelled (in Dollars per share)	$ 0
Awards outstanding, March 31, 2013	715,834
Awards outstanding, March 31, 2013 (in Dollars)	$ 1,367
Awards outstanding, March 31, 2013	1 year 171 days
Awards outstanding, March 31, 2013 (in Dollars per share)	$ 0
Awards vested and expected to vest at March 31, 2013	644,209
Awards vested and expected to vest at March 31, 2013 (in Dollars)	1,230
Awards vested and expected to vest at March 31, 2013	2 years 142 days
Awards vested and expected to vest at March 31, 2013 (in Dollars per share)	$ 0
Awards exercisable at March 31, 2013	0
Awards exercisable at March 31, 2013 (in Dollars per share)	$ 0
Awards exercisable at March 31, 2013 (in Dollars)	$ 0
Awards exercisable at March 31, 2013	0 years