Weighted Average Assumptions used in Determining Fair Value for Options Granted (Detail)	9 Months Ended
	Sep. 30, 2015 $ / shares
Schedule Of Weighted Average Assumptions For Fair Values Of Stock Options [Line Items]
Expected dividend yield	1.39%
Expected stock volatility	39.40%
Risk-free interest rate	1.88%
Expected holding period	6 years 10 months 20 days
Grant date fair value	$ 36.08