Other Comprehensive Income (Loss) (AOCI) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		$ 2,699.1
Other comprehensive income (loss) before reclassifications		(442.8)	$ (80.7)
Net amount reclassified from accumulated other comprehensive loss		80.5	133.4
Net other comprehensive income (loss)		(362.3)	52.7
Ending balance		3,197.2
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(6,523.6)	(5,740.2)
Ending balance		(6,885.9)	(5,687.5)
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(6,523.6)	(5,729.2)
Ending balance		(6,885.9)	(5,687.5)
AOCI Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			11.0
Continuing Operations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net other comprehensive income (loss)		(362.3)	(4.1)
Continuing Operations | Foreign Currency Translation Gains (Losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(1,678.0)	(1,569.7)
Other comprehensive income (loss) before reclassifications		(126.5)	(31.7)
Net amount reclassified from accumulated other comprehensive loss		0.0	0.0
Net other comprehensive income (loss)		(126.5)	(31.7)
Ending balance		(1,804.5)	(1,601.4)
Continuing Operations | Unrealized Net Gains (Losses) on Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		4.9	(22.1)
Other comprehensive income (loss) before reclassifications		1.0	16.8
Net amount reclassified from accumulated other comprehensive loss		(0.1)	1.7
Net other comprehensive income (loss)		0.9	18.5
Ending balance		5.8	(3.6)
Continuing Operations | Defined Benefit Pension and Retiree Health Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(4,638.6)	(3,852.7)
Other comprehensive income (loss) before reclassifications		30.9	(5.7)
Net amount reclassified from accumulated other comprehensive loss		77.4	44.7
Net other comprehensive income (loss)		108.3	39.0
Ending balance		(4,530.3)	(3,813.7)
Continuing Operations | Effective Portion of Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(211.9)	(238.9)
Other comprehensive income (loss) before reclassifications		(348.2)	(32.9)
Net amount reclassified from accumulated other comprehensive loss		3.2	3.0
Net other comprehensive income (loss)		(345.0)	(29.9)
Ending balance		(556.9)	(268.8)
Discontinued Operations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net other comprehensive income (loss)	[1]	0.0	56.8
Discontinued Operations | Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		0.0	(56.8)
Other comprehensive income (loss) before reclassifications		0.0	(27.2)
Net amount reclassified from accumulated other comprehensive loss		0.0	84.0
Net other comprehensive income (loss)		0.0	56.8
Ending balance		$ 0.0	$ 0.0

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