Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income (loss)	$ (71,492)	$ (29,260)	$ 15	$ 94	$ 1,302	$ 19,013	$ 36,137	$ 36,769	$ (100,639)	$ 93,221	$ 192,008
Weighted average basic common shares outstanding (in shares)									37,457,413	37,537,000	38,364,000
Effect of dilutive securities-stock options and awards (in shares)									0	130,000	167,000
Total shares and dilutive securities (in shares)									37,457,413	37,667,000	38,531,000
Basic earnings per common share (in dollars per share)	$ (1.90)	$ (0.78)	$ 0.00	$ 0.00	$ 0.03	$ 0.51	$ 0.96	$ 0.97	$ (2.69)	$ 2.48	$ 5.00
Diluted earnings per common share (in dollars per share)	$ (1.90)	$ (0.78)	$ 0.00	$ 0.00	$ 0.03	$ 0.51	$ 0.96	$ 0.97	$ (2.69)	$ 2.47	$ 4.98