Other Comprehensive Income (Loss) - Reclassification (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other–net, (income) expense	$ (20.9)	$ (0.1)	$ 0.1	$ (11.1)
Total before tax	1,588.4	427.2	7,641.7	4,045.8
Tax benefit	(618.1)	(484.6)	(1,461.5)	(995.1)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	23.8	15.9	81.4	21.7
Amortization of retirement benefit items | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	30.0	16.4	89.3	49.2
Tax benefit	(6.3)	(3.4)	(18.7)	(10.3)
Total reclassifications, net of tax	23.7	13.0	70.6	38.9
Prior service benefits, net | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other–net, (income) expense	(0.8)	(12.7)	(2.6)	(37.9)
Actuarial losses, net | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other–net, (income) expense	30.8	29.1	91.9	87.1
Other, net of tax | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other–net, (income) expense	$ 0.1	$ 2.9	$ 10.8	$ (17.2)