Earnings (Loss) per Share - Schedule of Earnings (Loss) per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Basic earnings (loss) per share, Net Income (Loss)	$ 22,697	$ (175,850)	$ (40,147)	$ (236,979)
Diluted earnings (loss) per share, Net Income (Loss)	$ 22,697	$ (175,850)	$ (40,147)	$ (236,979)
Basic earnings (loss) per share, Shares	86,399	85,745	86,305	85,560
Effect of dilutive incentive-based awards, Shares	486
Diluted earnings (loss) per share, Shares	86,885	85,745	86,305	85,560
Basic earnings (loss) per share, Per Share Amount	$ 0.26	$ (2.05)	$ (0.47)	$ (2.77)
Diluted earnings (loss) per share, Per Share Amount	$ 0.26	$ (2.05)	$ (0.47)	$ (2.77)