Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net (gain) loss	$ 1,565	$ (140)
Reclassification adjustments	10,877	10,921
Income before income taxes	(127,499)	(137,001)
Provision for income taxes	25,501	26,733
Net income	(101,998)	(110,268)
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	2,874	1,700
Reclassification out of Accumulated Other Comprehensive Income | Retirement Benefits Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	2,874	1,700
Provision for income taxes	(578)	(438)
Net income	2,296	1,262
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	1,545	1,588
Income before income taxes	1,545	1,588
Provision for income taxes	(351)	(361)
Net income	$ 1,194	$ 1,227