Earnings Per Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share Basic And Diluted [Abstract]
Net income	$ 126,172	$ 96,037	$ 74,806
Basic weighted average shares outstanding	36,844	36,690	36,930
Dilutive effect of stock options and restricted stock	894	947	959
Diluted weighted average shares outstanding	37,738	37,637	37,889
Basic earnings per share	$ 3.42	$ 2.62	$ 2.03
Diluted earnings per share	$ 3.34	$ 2.55	$ 1.97