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, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share Basic And Diluted [Abstract]
Net income from continuing operations	$ 96,037	$ 74,806	$ 68,563
Net income from discontinued operations			7,453
Net income	$ 96,037	$ 74,806	$ 76,016
Basic weighted average shares outstanding	36,690	36,930	36,886
Dilutive effect of stock options and restricted stock	947	959	1,002
Diluted weighted average shares outstanding	37,637	37,889	37,888
Income from continuing operations	$ 2.62	$ 2.03	$ 1.86
Income from discontinued operations			0.20
Net income per common share	2.62	2.03	2.06
Income from continuing operations	2.55	1.97	1.81
Income from discontinued operations			0.20
Net income per common share	$ 2.55	$ 1.97	$ 2.01