Employee Benefit Plans - Schedule of Stock Appreciation Rights Activity (Detail) - Stock appreciation rights (SARs) [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs Outstanding Beginning Balance	418,801
Number of SARs Granted	176,200
Number of SARs Exercised	(33,262)
Number of SARs Canceled	(31,038)
Number of SARs Outstanding Ending Balance	530,701
Weighted Average Grant Price Outstanding Beginning Balance	$ 43.55
Weighted Average Grant Price Granted	64.93
Weighted Average Grant Price Exercised	39.61
Weighted Average Grant Price Canceled	51.00
Weighted Average Grant Price Outstanding Ending Balance	$ 50.46
Aggregate Intrinsic Value	$ 9,659	$ 6,417