Earnings Per Share - Reconciliation of Numerators and Denominators of Basic and Diluted Per-Share Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income (loss) - basic and diluted numerator	$ 10,799	$ 13,927	$ 50,287	$ (488,585)
Weighted average shares - basic (denominator):	137,227	137,170	137,208	137,167
Dilutive effect of stock-based awards	14	84	29
Weighted average shares including conversions - diluted (denominator)	137,241	137,254	137,237	137,167
Earnings (loss) per share:
Basic	$ 0.08	$ 0.10	$ 0.37	$ (3.56)
Diluted	$ 0.08	$ 0.10	$ 0.37	$ (3.56)