Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial (gains) losses and prior service costs	$ 8.3	$ 0.0	$ 7.7	$ (2.3)
Total before tax	(178.5)	(177.1)	(358.3)	(357.5)
Provision for income taxes	40.0	39.0	80.0	79.5
Total net of tax	(138.6)	(138.2)	(278.4)	(278.2)
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 actuarial (gains) losses and prior service costs	(1.3)	1.1	(0.7)	1.9
Reclassification out of Accumulated Other Comprehensive Income | Retirement Benefits Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(1.3)	1.1	(0.7)	1.9
Provision for income taxes	0.4	(0.5)	0.2	(0.7)
Total net of tax	$ (0.9)	$ 0.6	$ (0.5)	$ 1.2