Earnings (Loss) Per Share - Reconciliation of Numerators and Denominators Used in Computations of Both Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic earnings (loss) per share computation:
Income (loss) from continuing operations	$ 33,519	$ 14,526	$ 33,371	$ 39,201	$ 18,818	$ 20,233	$ 26,519	$ (73,651)	$ 120,617	$ (8,081)	$ (20,187)
Average common shares - Basic (in shares)									90,933,886	93,298,467	93,916,656
Basic earnings (loss) per share from continuing operations (in dollars per share)									$ 1.33	$ (0.09)	$ (0.22)
Diluted earnings (loss) per share computation:
Income (loss) from continuing operations	$ 33,519	$ 14,526	$ 33,371	$ 39,201	$ 18,818	$ 20,233	$ 26,519	$ (73,651)	$ 120,617	$ (8,081)	$ (20,187)
Stock option conversion (in shares)									246,116	0	0
RSUs and PSUs (in shares)									330,481	0	0
Average common shares - diluted (in shares)									91,510,483	93,298,467	93,916,656
Diluted earnings (loss) per share from continuing operations (in dollars per share)									$ 1.32	$ (0.09)	$ (0.22)
Common Stock
Diluted earnings (loss) per share computation:
Anti-dilutive options excluded (in shares)									1,262,158	2,933,770	3,840,637
Stock Units
Diluted earnings (loss) per share computation:
Anti-dilutive options excluded (in shares)									0	340,398	312,971