Weighted-Average Assumptions Used to Estimate Grant Date Fair Values for Stock Options Granted (Detail) (Employee Stock Option)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Method Used [Line Items]
Volatility	35.64%		35.89%	41.36%
Expected term (in years)	5 years		5 years	5 years
Dividend yield	1.18%		1.17%	0.89%
Risk-free interest rate	1.62%		1.76%	0.70%