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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Basic earnings (loss) per share, Net Income (Loss)	$ 5,809	$ 37,406	$ (37,789)	$ (11,811)
Diluted earnings (loss) per share, Net Income (Loss)	$ 5,809	$ 37,406	$ (37,789)	$ (11,811)
Basic earnings (loss) per share, Shares	86,186	86,877	86,142	87,642
Effect of dilutive incentive-based awards, Shares	105	312
Diluted earnings (loss) per share, Shares	86,291	87,189	86,142	87,642
Basic earnings (loss) per share, Per Share Amount	$ 0.07	$ 0.43	$ (0.44)	$ (0.13)
Diluted earnings (loss) per share, Per Share Amount	$ 0.07	$ 0.43	$ (0.44)	$ (0.13)