Long-Term Incentive Employee Compensation Stock Option Grant Date Fair Value Weighted Average Assumptions (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	1.10%	1.00%	1.50%
Expected volatility	29.40%	29.60%	29.90%
Expected life	5 years 10 months	5 years 9 months 15 days	6 years 4 months 24 days
Risk-free rates	1.70%	1.80%	1.10%
Weighted-average grant date fair value	$ 11.23	$ 11.93	$ 6.62