Quarterly Financial Data - Summary of Condensed Quarterly Results of Operations (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
Quarterly Financial Information Disclosure [Abstract]
Operating revenues, net	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
(Loss) gain on disposition of assets, net	287	4	7	0	(504)	(85)	4,298	(359)	(298)	3,350	(339)
(Loss) earnings before income taxes	(20,319)	(4,899)	(3,150)	(23,073)	(12,012)	(7,766)	117	(7,488)	(51,441)	(27,149)	43,256
Net earnings (loss)	$ 29,330	$ (3,277)	$ (3,273)	$ (15,248)	$ (17,058)	$ (4,967)	$ 4,277	$ (8,932)	$ 7,532	$ (26,680)	$ 26,924
Net (loss) earnings per share
Basic (USD per share)	$ 1.87	$ (0.21)	$ (0.21)	$ (0.97)	$ (1.08)	$ (0.32)	$ 0.27	$ (0.57)	$ 0.48	$ (1.70)	$ 1.73
Diluted (USD per share)	$ 1.87	$ (0.21)	$ (0.21)	$ (0.97)	$ (1.08)	$ (0.32)	$ 0.27	$ (0.57)	$ 0.48	$ (1.70)	$ 1.72