Retirement Benefits (Schedule of Expected Benefit Payments, Contributions and Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 2,395.3	$ 2,211.2
Fair value of plan assets	1,035.4	977.1
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Fair value of plan assets	1,035.4	977.1
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax [Abstract]
Total other comprehensive income (loss) during period	(776.5)	616.9	$ 2,699.4
Defined Benefit Pension Plans
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023	661.2
2024	671.4
2025	695.0
2026	722.5
2027	746.5
2029-2033	4,160.7
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Fair value of plan assets	564.3	652.7
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	1,659.5	1,721.7
Fair value of plan assets	564.3	652.7
Components of net periodic (benefit) cost:
Service cost	290.4	351.7	369.2
Interest cost	648.2	398.1	337.8
Expected return on plan assets	(1,055.0)	(947.6)	(949.3)
Amortization of prior service (benefit) cost	2.4	2.4	4.2
Recognized actuarial (gain) loss	122.0	342.4	487.7
Net periodic (benefit) cost	8.0	147.0	249.6
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax [Abstract]
Actuarial gain (loss) arising during period	(763.9)	823.6	2,072.4
Amortization of prior service (benefit) cost included in net income	2.4	2.4	4.2
Amortization of net actuarial (gain) loss included in net income	122.0	342.4	487.7
Foreign currency exchange rate changes and other	(29.2)	55.5	47.2
Total other comprehensive income (loss) during period	(668.7)	1,223.9	2,611.5
Retiree Health Benefit Plans
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2023	93.8
2024	94.5
2025	94.7
2026	95.2
2027	95.6
2029-2033	475.9
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Fair value of plan assets	0.0	0.0
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	157.7	149.8
Fair value of plan assets	0.0	0.0
Components of net periodic (benefit) cost:
Service cost	31.8	46.6	49.2
Interest cost	61.3	37.8	32.5
Expected return on plan assets	(182.1)	(152.1)	(146.2)
Amortization of prior service (benefit) cost	(52.9)	(54.8)	(59.6)
Recognized actuarial (gain) loss	(5.8)	0.9	3.2
Net periodic (benefit) cost	(147.7)	(121.6)	(120.9)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax [Abstract]
Actuarial gain (loss) arising during period	(49.8)	(552.2)	142.5
Amortization of prior service (benefit) cost included in net income	(52.9)	(54.8)	(59.6)
Amortization of net actuarial (gain) loss included in net income	(5.8)	0.9	3.2
Foreign currency exchange rate changes and other	0.7	(0.9)	1.9
Total other comprehensive income (loss) during period	$ (107.8)	$ (607.0)	$ 88.0