Accumulated Other Comprehensive (Loss) Income - Summary of Amounts Reclassified (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee benefit costs:
Miscellaneous loss, net	$ 368			$ 1,523			$ 1,088	$ 2,912
Loss from continuing operations before income taxes	(68,682)			(46,663)			(348,946)	(20,151)
Income tax expense	(45)			(3,102)			(2,200)	(8,880)
Net loss	(68,637)	$ (238,301)	$ (39,808)	(68,532)	$ (113,661)	$ 6,815	(346,746)	(175,378)
Amounts reclassified from accumulated other comprehensive (loss) income | Amortization of actuarial loss
Employee benefit costs:
Miscellaneous loss, net	1,101			258			2,829	719
Amounts reclassified from accumulated other comprehensive (loss) income | Settlement
Employee benefit costs:
Miscellaneous loss, net	32			0			1,327	0
Amounts reclassified from accumulated other comprehensive (loss) income | Employee benefit costs
Employee benefit costs:
Loss from continuing operations before income taxes	1,133			258			4,156	719
Income tax expense	0			67			0	187
Net loss	$ 1,133			$ 191			$ 4,156	$ 532