Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail)

v3.5.0.2
Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail) - Nonqualified Stock Options [Member]
3 Months Ended 12 Months Ended
Sep. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Stockholders Equity Note [Line Items]      
Expected life (in years) 7 years 6 months 7 years 6 months 7 years 6 months
Risk-free interest rate 1.50% 1.66% 2.07%
Expected volatility 19.10% 23.60% 20.61%
Expected dividend yield 2.97% 2.94% 2.63%