Accumulated Other Comprehensive (Loss) Income - Summary of Amounts Reclassified (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee benefit costs:
Miscellaneous loss, net	$ 188		$ (523)		$ (720)	$ (1,389)
(Loss) income from continuing operations before income taxes	(238,268)		23,300		(280,264)	26,512
Income tax (expense) benefit	(33)		1,000		2,155	5,778
Net loss	(238,301)	$ (39,808)	(113,661)	$ 6,815	(278,109)	(106,846)
Amounts reclassified from accumulated other comprehensive (loss) income | Amortization of actuarial loss
Employee benefit costs:
Miscellaneous loss, net	934		222		1,728	461
Amounts reclassified from accumulated other comprehensive (loss) income | Settlement
Employee benefit costs:
Miscellaneous loss, net	95		0		1,295	0
Amounts reclassified from accumulated other comprehensive (loss) income | Employee benefit costs
Employee benefit costs:
(Loss) income from continuing operations before income taxes	1,029		222		3,023	461
Income tax (expense) benefit	0		(58)		0	(120)
Net loss	$ 1,029		$ 164		$ 3,023	$ 341