Accumulated Other Comprehensive Loss - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassifications out of accumulated other comprehensive income (loss):
Income tax benefit	$ (55,661)	$ 33,675	$ (77,710)	$ 9,018
Total reclassifications			(1,081)
Defined Benefit Plans
Reclassifications out of accumulated other comprehensive income (loss):
Total reclassifications			(515)
Reclassification out of Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income (loss):
Total reclassifications	12,186	146	12,289	289
Reclassification out of Accumulated Other Comprehensive Income | Amortization of loss on interest rate hedge
Reclassifications out of accumulated other comprehensive income (loss):
Operating expenses	15,972		15,852
Income tax benefit	(3,980)		(3,950)
Total reclassifications	11,992		11,902
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	258	192	515	384
Income tax benefit	(64)	(46)	(128)	(95)
Total reclassifications	$ 194	$ 146	$ 387	$ 289