Share-Based Compensation (Fair Value Assumptions) (Detail)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate of return	0.68%	0.89%
Expected dividend yields	1.63%	1.37%
Expected award life (years)	5 years 11 days	5 years 15 days
Expected volatility	32.50%	32.10%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate of return	1.11%	2.07%
Expected dividend yields	1.67%	1.54%
Expected award life (years)	5 years 15 days	5 years 26 days
Expected volatility	32.80%	32.50%