Share-Based Compensation - Schedule of Weighted Average Option Fair Values and Assumptions (Detail) - Stock Option - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of grants (in dollars per share)	$ 21.88	$ 19.98	$ 18.47	$ 20.34
Dividend yield	1.53%	1.65%	1.69%	1.44%
Volatility	29.60%	29.64%	29.71%	29.91%
Risk-free interest rate, minimum	0.51%	0.29%	0.53%	0.24%
Risk-free interest rate, maximum	2.01%	3.37%	2.50%	2.82%
Expected life (in years)	5 years 10 months 28 days	6 years 1 month 28 days	5 years 10 months 28 days	5 years 11 months 5 days