Stock-Based Compensation - Fair Value of Date of Grant Using Black-Scholes Option-Pricing Model (Detail) - Stock Options [Member]	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Dividend yield	3.40%	2.20%
Risk-free interest rate	0.60%	0.50%
Expected volatility	34.00%	34.00%
Expected life (in years)	5 years 2 months 12 days	5 years 2 months 12 days