Other Comprehensive Income (Loss) (Reclassification) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other–net, (income) expense	$ 20.1	$ (13.0)	$ 34.1	$ (161.5)
Total before tax	1,245.3	1,437.2	4,315.6	4,760.8
Tax benefit	(135.2)	(228.8)	(460.0)	(683.9)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	89.4	33.4	269.2	202.8
Defined Benefit Pension and Retiree Health Benefit Plans | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	108.8	38.3	327.2	240.2
Tax benefit	(22.8)	(8.0)	(68.7)	(50.4)
Total reclassifications, net of tax	86.0	30.3	258.5	189.8
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	(13.9)	(20.8)	(41.5)	(48.4)
Actuarial losses, net | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other–net, (income) expense	122.7	59.1	368.7	288.6
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	$ 3.4	$ 3.1	$ 10.7	$ 13.0