Stock Option Plans - Black-Scholes Option Pricing Model with Weighted Average (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected dividend yield	3.50%	4.00%	4.50%
Expected risk-free interest rate	1.20%	1.20%	2.70%
Volatility	29.60%	26.90%	26.80%
Expected life (in years)	6 years	5 years	6 years