Stock-Based Compensation - Activity of Options Outstanding not yet Vested (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares, Unvested as of December 31, 2011	1,640
Number of Shares, Granted	613	578	539
Number of Shares, Vesting during period	(718)
Number of Shares, Forfeited or cancelled	(9)
Number of Shares, Unvested as of December 31, 2012	1,526	1,640
Weighted-Average Grant Date Fair Value Per Share, Unvested as of December 31, 2011	$ 14.00
Weighted-Average Grant Date Fair Value Per Share, Granted	$ 20.31	$ 18.53	$ 15.88
Weighted-Average Grant Date Fair Value Per Share, Vesting during period	$ 12.58
Weighted-Average Grant Date Fair Value Per Share, Forfeited or canceled	$ 15.20
Weighted-Average Grant Date Fair Value Per Share, Unvested as of December 31, 2012	$ 17.20	$ 14.00