Accumulated Other Comprehensive Loss - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassifications out of accumulated other comprehensive income (loss):
Income tax benefit	$ (36,243)	$ 61,626	$ (113,953)	$ 70,644
Total reclassifications			(2,248)
Defined Benefit Plans
Reclassifications out of accumulated other comprehensive income (loss):
Total reclassifications			(750)
Reclassification out of Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income (loss):
Total reclassifications	1,167	151	13,456	440
Reclassification out of Accumulated Other Comprehensive Income | Amortization of loss on interest rate hedge
Reclassifications out of accumulated other comprehensive income (loss):
Operating expenses	1,320		17,172
Income tax benefit	(329)		(4,279)
Total reclassifications	991		12,893
Reclassification out of Accumulated Other Comprehensive Income | Amortization of deferred actuarial loss and prior service cost
Reclassifications out of accumulated other comprehensive income (loss):
Operating expenses	235	205	750	589
Income tax benefit	(59)	55	(187)	(40)
Total reclassifications	$ 176	$ 151	$ 563	$ 440