Other Comprehensive Income (Loss) (Schedule of Component of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 2,699.1
Other comprehensive income (loss) before reclassifications	(256.2)	$ (997.6)	$ (106.9)
Net amount reclassified from accumulated other comprehensive loss	283.4	214.2	190.5
Net other comprehensive income (loss)	27.2	(783.4)	83.6
Ending balance	5,825.2	2,699.1
Accumulated other comprehensive income (loss)	(6,496.4)	(6,523.6)
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(6,523.6)	(5,740.2)	(5,694.9)
Reclassification due to adoption of new accounting standard			(128.9)
Ending balance	(6,496.4)	(6,523.6)	(5,740.2)
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(6,523.6)	(5,729.2)	(5,718.6)
Reclassification due to adoption of new accounting standard			105.2
Ending balance	(6,496.4)	(6,523.6)	(5,729.2)
AOCI Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)			(11.0)	$ 23.7
Continuing Operations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net other comprehensive income (loss)	27.2	(840.2)	69.3
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)	(1,191.7)
Other comprehensive income (loss) before reclassifications	250.5	(46.2)	(378.0)
Net amount reclassified from accumulated other comprehensive loss	0.0	(62.1)	0.0
Net other comprehensive income (loss)	250.5	(108.3)	(378.0)
Ending balance	(1,427.5)	(1,678.0)	(1,569.7)
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)	113.5
Reclassification due to adoption of new accounting standard			(128.9)
Other comprehensive income (loss) before reclassifications	6.8	28.9	24.5
Net amount reclassified from accumulated other comprehensive loss	3.1	(1.9)	(31.2)
Net other comprehensive income (loss)	9.9	27.0	(6.7)
Ending balance	14.8	4.9	(22.1)
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)	(4,311.3)
Other comprehensive income (loss) before reclassifications	(379.7)	(967.6)	250.7
Net amount reclassified from accumulated other comprehensive loss	267.3	181.7	207.9
Net other comprehensive income (loss)	(112.4)	(785.9)	458.6
Ending balance	(4,751.0)	(4,638.6)	(3,852.7)
Continuing Operations | Effective Portion of Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(238.9)	(234.3)
Other comprehensive income (loss) before reclassifications		14.5	(16.3)
Net amount reclassified from accumulated other comprehensive loss		12.5	11.7
Net other comprehensive income (loss)		27.0	(4.6)
Ending balance			(238.9)
Continuing Operations | Effective Portion of Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(211.9)
Other comprehensive income (loss) before reclassifications	(133.8)
Net amount reclassified from accumulated other comprehensive loss	13.0
Net other comprehensive income (loss)	(120.8)
Ending balance	(332.7)	(211.9)
Discontinued Operations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net other comprehensive income (loss)	0.0	56.8	14.3
Discontinued Operations | Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	0.0	(56.8)	(71.1)
Other comprehensive income (loss) before reclassifications	0.0	(27.2)	12.2
Net amount reclassified from accumulated other comprehensive loss	0.0	84.0	2.1
Net other comprehensive income (loss)	0.0	56.8	14.3
Ending balance	$ 0.0	$ 0.0	$ (56.8)