Earnings 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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings per common share—basic
Net income	$ 34,105	$ 12,818	$ 72,495	$ 48,637
Weighted-average common shares outstanding—basic (in shares)	94,029	78,395	93,990	78,076
Basic earnings per common share (in dollars per share)	$ 0.36	$ 0.16	$ 0.77	$ 0.62
Earnings per common share—diluted
Net income	$ 34,105	$ 12,818	$ 72,495	$ 48,637
Add: Interest on convertible debt	0	1,260	0	2,506
Net income including assumed conversions	$ 34,105	$ 14,078	$ 72,495	$ 51,143
Weighted-average common shares outstanding—basic (in shares)	94,029	78,395	93,990	78,076
Convertible notes weighted-average shares outstanding (in shares)	0	15,000	0	15,000
Options, restricted stock and other dilutive securities (in shares)	1,864	1,518	1,668	1,330
Weighted-average common shares outstanding—diluted (in shares)	95,893	94,913	95,658	94,406
Dilutive earnings per common share (in dollars per share)	$ 0.36	$ 0.15	$ 0.76	$ 0.54