Share-Based Compensation - Weighted Average Fair Values and Related Assumptions for Options Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation [Abstract]
Fair value per share (usd per share)	$ 7.69	$ 7.28	$ 5.15
Expected dividend yield (percent)	1.75%	1.86%	2.40%
Risk free interest rate (percent)	1.60%	1.65%	1.26%
Expected volatility factor (percent)	36.61%	39.23%	37.59%
Expected life in years	6 years	5 years 7 months 30 days	6 years 3 months 30 days