Other Comprehensive Loss - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net (gain) loss	$ (1.0)	$ 0.6	$ (3.3)	$ 17.0
Reclassification adjustments	9.6	9.5	28.6	31.4
Total before tax	228.4	151.1	585.9	426.6
Provision for income taxes	49.7	35.4	129.2	96.0
Net income	(178.7)	(115.7)	(456.9)	(330.6)
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	0.6	1.1	2.5	14.2
Reclassification out of Accumulated Other Comprehensive Income | Retirement Benefits Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0.6	1.1	2.5	14.2
Provision for income taxes	0.0	(0.3)	(0.7)	(3.4)
Net income	0.6	0.8	1.8	10.8
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	0.0	0.0	0.0	3.2
Total before tax	0.0	0.0	0.0	3.2
Provision for income taxes	0.0	0.0	0.0	(0.7)
Net income	$ 0.0	$ 0.0	$ 0.0	$ 2.5