Stock-Based Compensation - Weighted Average Assumptions in Valuation Model (Detail) - Stock Options [Member]	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected holding period (in years)	5 years	5 years 6 months	5 years 7 months 6 days
Expected volatility	21.40%	24.40%	26.40%
Expected dividend yield	2.40%	2.70%	3.60%
Risk-free interest rate	1.50%	1.70%	1.00%