Stock-Based Incentive Plan - Aggregated Assumptions Used to Estimate Fair Value of Options Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life in years		8 years	8 years 2 months 12 days
Expected option life in years - weighted average	7 years 10 months 24 days
Risk free interest rate		1.64%	2.51%
Risk free interest rate - weighted average	1.87%
Expected dividend yield		4.32%	4.26%
Expected dividend yield - weighted average	4.06%
Expected volatility		49.38%	50.16%
Expected volatility - weighted average	45.82%
Fair value of options	$ 6.23	$ 6.07	$ 6.53
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life in years	7 years 7 months 6 days
Risk free interest rate	1.38%
Expected dividend yield	3.80%
Expected volatility	37.71%
Fair value of options	$ 5.40
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life in years	8 years 2 months 12 days
Risk free interest rate	1.89%
Expected dividend yield	4.19%
Expected volatility	46.22%
Fair value of options	$ 6.27