Share-Based Compensation - Schedule of Fair Value of Each Stock Option Award is Estimated on Grant Date, Using Option Valuation Models (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Weighted Average Assumptions For Fair Values Of Stock Options [Line Items]
Risk-free interest rate	1.18%	0.89%	2.07%
Expected volatility	50.00%	41.00%	35.00%
Expected life, in years	6 years 3 months	5 years	5 years
Expected dividend yield