Earnings (Loss) per Share - Schedule of Computation of Basic and Diluted Earnings (Loss) Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income (loss)	$ 43,653	$ 5,604	$ (8,059)	$ 43,738	$ (49,790)	$ 29,866	$ (17,816)	$ 8,125	$ 84,936	$ (29,615)	$ (84,867)
Basic weighted average common stock outstanding	34,176,812	34,103,029	33,952,574	33,662,297	35,068,330	34,849,805	34,716,081	34,698,904	33,943,264	34,833,967	34,380,517
Basic earnings (loss) per share	$ 1.28	$ 0.16	$ (0.24)	$ 1.30	$ (1.42)	$ 0.86	$ (0.51)	$ 0.23	$ 2.50	$ (0.85)	$ (2.47)
Diluted Earnings per Share
Net income (loss)	$ 43,653	$ 5,604	$ (8,059)	$ 43,738	$ (49,790)	$ 29,866	$ (17,816)	$ 8,125	$ 84,936	$ (29,615)	$ (84,867)
Add back: Interest expense on Exchangeable Notes									5,349
Net income (loss) allocated to common stockholders									$ 90,285	$ (29,615)	$ (84,867)
Basic weighted average common stock outstanding	34,176,812	34,103,029	33,952,574	33,662,297	35,068,330	34,849,805	34,716,081	34,698,904	33,943,264	34,833,967	34,380,517
Net effect of dilutive equity awards									821,664
Net effect of assumed conversion of 5.0% Exchangeable Notes to common stock									9,990,209
Diluted weighted average common stock outstanding	45,573,889	45,542,418	33,952,574	42,892,044	35,068,330	35,302,706	34,716,081	34,918,568	44,755,137	34,833,967	34,380,517
Diluted earnings (loss) per share	$ 0.99	$ 0.15	$ (0.24)	$ 1.05	$ (1.42)	$ 0.85	$ (0.51)	$ 0.23	$ 2.02	$ (0.85)	$ (2.47)