Weighted-Average Assumptions Used for Options Granted (Detail) - Equity Option	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected Term (in Years)	7 years 1 month 6 days	7 years 3 months 18 days	7 years 7 months 6 days
Dividend Yield	2.07%	2.16%	2.38%
Expected Volatility	30.40%	30.10%	29.50%
Risk-Free Interest Rate	1.83%	2.02%	1.43%