(Loss) Earnings Per Share - Schedule of (Loss) Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Basic (loss) earnings per share, Net (Loss)	$ (15,854)	$ 39,120	$ (56,214)	$ (6,014)
Effect of dilutive incentive-based awards
Diluted (loss) earnings per share, Net (Loss)	$ (15,854)	$ 39,120	$ (56,214)	$ (6,014)
Basic (loss) earnings per share, Shares	88,222	82,448	85,510	82,436
Effect of dilutive incentive-based awards, Shares		792
Diluted (loss) earnings per share, Shares	88,222	83,240	85,510	82,436
Basic (loss) earnings per share, Per Share Amount	$ (0.18)	$ 0.47	$ (0.66)	$ (0.07)
Effect of dilutive incentive-based awards, per share
Diluted (loss) earnings per share, Per Share Amount	$ (0.18)	$ 0.47	$ (0.66)	$ (0.07)