Earnings (Loss) per Common Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings per common share—basic
Net income	$ 31,443	$ 34,105	$ 57,132	$ 72,495
Weighted-average common shares outstanding—basic (in shares)	94,213	94,029	94,142	93,990
Basic earnings per common share (usd per share)	$ 0.33	$ 0.36	$ 0.61	$ 0.77
Earnings per common share—diluted
Weighted-average common shares outstanding—basic (in shares)	94,213	94,029	94,142	93,990
Options and restricted stock (in shares)	1,984	1,864	1,931	1,668
Weighted-average common shares outstanding—diluted (in shares)	96,197	95,893	96,073	95,658
Dilutive earnings (loss) per common share (usd per share)	$ 0.33	$ 0.36	$ 0.59	$ 0.76