Retirement Benefits (Schedule of Expected Benefit Payments, Contributions and Expense) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation		$ 14,039.7	$ 11,584.2
Fair value of plan assets		10,483.4	8,895.6
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Fair value of plan assets		10,483.4	8,895.6
Components of net periodic (benefit) cost:
Curtailment (gain) loss	$ (28.0)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax [Abstract]
Total other comprehensive income (loss) during period		(970.0)	544.0	$ (566.8)
Defined Benefit Pension Plans
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2020		614.5
2021		621.8
2022		641.0
2023		652.3
2024		682.4
2025-2029		3,712.1
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Fair value of plan assets		10,483.4	8,895.6
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation		13,063.7	10,837.8
Fair value of plan assets		10,483.4	8,895.6
Components of net periodic (benefit) cost:
Service cost		250.4	292.7	320.8
Interest cost		486.0	458.5	411.6
Expected return on plan assets		(839.6)	(842.1)	(773.6)
Amortization of prior service (benefit) cost		6.1	4.6	5.6
Recognized actuarial loss		284.9	332.5	286.8
Curtailment (gain) loss		2.2	1.3	93.5
Special termination benefit		0.0	0.0	317.2
Net periodic (benefit) cost		190.0	247.5	661.9
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax [Abstract]
Actuarial gain (loss) arising during period		(1,461.0)	182.8	(898.1)
Plan amendments during period		0.0	(17.6)	0.0
Curtailment gain (loss)		19.0	45.2	3.2
Amortization of prior service (benefit) cost included in net income		6.1	4.6	5.6
Amortization of net actuarial loss included in net income		284.9	332.5	286.8
Foreign currency exchange rate changes and other		(7.7)	47.1	(108.8)
Total other comprehensive income (loss) during period		(1,158.7)	594.6	(711.3)
Retiree Health Benefit Plans
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2020		93.7
2021		93.8
2022		92.9
2023		91.7
2024		94.3
2025-2029		469.8
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		214.4	189.4
Fair value of plan assets		0.0	0.0
Components of net periodic (benefit) cost:
Service cost		36.3	41.5	46.4
Interest cost		58.0	57.3	52.9
Expected return on plan assets		(144.3)	(177.9)	(160.7)
Amortization of prior service (benefit) cost		(62.9)	(79.5)	(90.0)
Recognized actuarial loss		1.9	6.1	18.4
Curtailment (gain) loss		0.0	(29.3)	65.5
Special termination benefit		0.0	0.0	37.5
Net periodic (benefit) cost		(111.0)	(181.8)	(30.0)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax [Abstract]
Actuarial gain (loss) arising during period		246.1	37.5	261.3
Plan amendments during period		0.0	14.1	0.0
Curtailment gain (loss)		0.0	(31.8)	(39.7)
Amortization of prior service (benefit) cost included in net income		(62.9)	(79.5)	(90.0)
Amortization of net actuarial loss included in net income		1.9	6.1	18.4
Foreign currency exchange rate changes and other		3.6	(0.1)	(3.3)
Total other comprehensive income (loss) during period		$ 188.7	$ (53.7)	$ 146.7