Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (16,832)	$ 6,560
Other comprehensive (loss) income, net of tax:
Net loss arising during the period, net of tax benefit of $6,817 and $0	(19,402)
Effect of pension settlement, net of tax benefit of $11,177 and $0	31,811
Amortization of prior service credit included in net (loss) income, net of tax benefit of $76 and $561	(215)	(1,597)
Amortization of actuarial loss included in net (loss) income, net of tax expense of $1,189 and $971	3,384	2,763
Cash flow hedges, net of tax benefit of $1,810 and $364	(38,525)	(8,513)
Other comprehensive loss, net of tax	(22,947)	(7,347)
Comprehensive loss	$ (39,779)	$ (787)