Weighted Average Black-Scholes Fair Value Assumptions used in Valuation of Stock Options Granted (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Dividend yield	1.20%	1.40%	1.10%
Expected volatility	50.60%	48.50%	46.20%
Risk-free interest rate	0.80%	2.00%	2.20%
Expected life	4 years 10 months 24 days	5 years	4 years 8 months 12 days