Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net (gain) loss	$ (848)	$ 1,565
Reclassification adjustments	10,776	10,877
Income before income taxes	(145,619)	(127,499)
Provision for income taxes	32,947	25,501
Net income	(112,708)	(101,998)
Reclassification out of Accumulated Other Comprehensive Income | Net Prior Service Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net (gain) loss	1,054	2,874
Reclassification out of Accumulated Other Comprehensive Income | Retirement Benefits Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	1,054	2,874
Provision for income taxes	(309)	(578)
Net income	745	2,296
Reclassification out of Accumulated Other Comprehensive Income | Cumulative Unrealized Gain (Loss) on Derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustments	859	1,545
Income before income taxes	859	1,545
Provision for income taxes	(195)	(351)
Net income	$ 664	$ 1,194