Earnings (Loss) per Share - Schedule of Earnings (Loss) per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Basic earnings (loss) per share, Net Income (Loss)	$ 95,988	$ 55,034	$ 55,841	$ (181,945)
Diluted earnings (loss) per share, Net Income (Loss)	$ 95,988	$ 55,034	$ 55,841	$ (181,945)
Basic earnings (loss) per share, Shares	86,616	86,012	86,410	85,712
Effect of dilutive incentive-based awards, Shares	926	272	619
Diluted earnings (loss) per share, Shares	87,542	86,284	87,029	85,712
Basic earnings (loss) per share, Per Share Amount	$ 1.11	$ 0.64	$ 0.65	$ (2.12)
Diluted earnings (loss) per share, Per Share Amount	$ 1.10	$ 0.64	$ 0.64	$ (2.12)