Stock Options and Other Equity-Based Incentive Instruments - Weighted-Average Assumptions Used to Determine Fair Value of Options Granted (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assumptions used to value option grants:
Average expected terms (years)	0 years	6 years 3 months 18 days	7 years
Volatility		42.10%	56.20%
Annual rate of dividends		1.90%	1.87%
Discount rate		1.69%	1.26%