Stock-Based Compensation - SAR Activity (Detail) - Stock Appreciation Rights [Member] - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Stock Appreciation Rights Activity [Line Items]
SARs Outstanding, Beginning Balance	262,077	515,830	739,194
Granted, SARs		15,585	3,866
Exercised, SARs	(124,352)	(263,626)	(218,826)
Canceled, SARs		(5,712)	(8,404)
Shares Outstanding, SARs, Ending Balance	137,725	262,077	515,830
Outstanding, Weighted Average Grant Price Per Share, Beginning Balance	$ 13.13	$ 13.98	$ 12.93
Vested, SARs	127,469
Granted, Weighted Average Grant Price Per Share		41.19	37.88
Exercisable, SARs	127,469
Exercised, Weighted Average Grant Price Per Share	$ 11.09	13.86	10.96
Canceled, Weighted Average Grant Price Per Share		21.94	4.74
Outstanding, Weighted Average Grant Price Per Share, Ending Balance	19.57	$ 13.13	$ 13.98
Vested, Weighted Average Grant Price Per Share	17.83
Exercisable, Weighted Average Grant Price Per Share	$ 17.83
Weighted Average Remaining Contractual Life, Outstanding	5 years 7 months 6 days
Weighted Average Remaining Contractual Life, Vested	5 years 4 months 24 days
Weighted Average Remaining Contractual Life, Exercisable	5 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding	$ 6,174,886
Aggregate Intrinsic Value, Vested	5,936,639
Aggregate Intrinsic Value, Exercisable	$ 5,936,639