Other Comprehensive Income (Loss) (AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			$ 5,825.2
Other comprehensive income (loss) before reclassifications	$ 25.0	$ 94.4	54.5	$ (234.3)
Net amount reclassified from accumulated other comprehensive loss	89.4	33.4	269.2	202.8
Net other comprehensive income (loss)	114.4	127.8	323.7	(31.5)
Ending balance	7,954.1		7,954.1
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(6,287.1)	(6,682.9)	(6,496.4)	(6,523.6)
Ending balance	(6,172.7)	(6,555.1)	(6,172.7)	(6,555.1)
Foreign Currency Translation Gains (Losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,516.2)	(1,722.5)	(1,427.5)	(1,678.0)
Other comprehensive income (loss) before reclassifications	(8.0)	30.3	(96.7)	(14.2)
Net amount reclassified from accumulated other comprehensive loss	0.0	0.0	0.0	0.0
Net other comprehensive income (loss)	(8.0)	30.3	(96.7)	(14.2)
Ending balance	(1,524.2)	(1,692.2)	(1,524.2)	(1,692.2)
Unrealized Net Gains (Losses) on Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	9.1	15.1	14.8	4.9
Other comprehensive income (loss) before reclassifications	(2.4)	0.8	(8.8)	7.6
Net amount reclassified from accumulated other comprehensive loss	0.1	(0.2)	0.8	3.2
Net other comprehensive income (loss)	(2.3)	0.6	(8.0)	10.8
Ending balance	6.8	15.7	6.8	15.7
Defined Benefit Pension and Retiree Health Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4,569.9)	(4,454.9)	(4,751.0)	(4,638.6)
Other comprehensive income (loss) before reclassifications	18.6	(19.6)	27.2	4.6
Net amount reclassified from accumulated other comprehensive loss	86.0	30.3	258.5	189.8
Net other comprehensive income (loss)	104.6	10.7	285.7	194.4
Ending balance	(4,465.3)	(4,444.2)	(4,465.3)	(4,444.2)
Effective Portion of Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(210.1)	(520.6)	(332.7)	(211.9)
Other comprehensive income (loss) before reclassifications	16.8	82.9	132.8	(232.3)
Net amount reclassified from accumulated other comprehensive loss	3.3	3.3	9.9	9.8
Net other comprehensive income (loss)	20.1	86.2	142.7	(222.5)
Ending balance	$ (190.0)	$ (434.4)	$ (190.0)	$ (434.4)