Share-Based Compensation - Schedule of Weighted Average Option Fair Values and Assumptions (Detail) - Stock Option - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of grants	$ 20.60	$ 19.49	$ 18.41	$ 20.39
Dividend yield	1.63%	1.65%	1.70%	1.42%
Volatility	29.62%	29.87%	29.71%	29.94%
Risk-free interest rate, minimum	0.60%	0.26%	0.53%	0.23%
Risk-free interest rate, maximum	2.56%	3.11%	2.50%	2.75%
Expected life (in years)	5 years 10 months 28 days	5 years 10 months 24 days	5 years 10 months 28 days	5 years 10 months 24 days