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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic earnings (loss) per share computation:
Income	$ 17,647	$ 33,371	$ 7,888	$ 72,572
Average common shares	90,882,415	91,244,745	90,796,585	91,406,969
Basic earnings per share from continuing operations (in dollars per share)	$ 0.19	$ 0.37	$ 0.09	$ 0.79
Diluted earnings (loss) per share computation:
Income	$ 17,647	$ 33,371	$ 7,888	$ 72,572
Average common shares	90,882,415	91,244,745	90,796,585	91,406,969
Average common shares — diluted	91,369,030	91,679,813	91,365,946	91,995,078
Diluted earnings per share from continuing operations (in dollars per share)	$ 0.19	$ 0.36	$ 0.09	$ 0.79
Stock options
Diluted earnings (loss) per share computation:
Stock option conversion	220,318	232,113	232,495	258,164
RSUs and PSUs
Diluted earnings (loss) per share computation:
Stock option conversion	266,297	202,955	336,866	329,945
Stock options
Diluted earnings (loss) per share computation:
Anti-dilutive securities excluded	655,700	1,282,259	776,710	1,349,300
RSUs and PSUs
Diluted earnings (loss) per share computation:
Anti-dilutive securities excluded	8,959	5,911	4,504	0