Other Comprehensive Income (Loss) (AOCI) (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance						$ 10,909.1
Reclassification due to adoption of new accounting standard								$ (128.9)
Other comprehensive income (loss) before reclassifications		$ 37.1		$ (700.4)		(43.6)	$ (375.8)
Net amount reclassified from accumulated other comprehensive loss		49.9		29.2		183.3	90.9
Net other comprehensive income (loss)		87.0	[1]	(671.2)	[1]	139.7	(284.9)
Ending balance		2,857.3				2,857.3
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(5,687.5)		(5,437.5)		(5,740.2)	(5,694.9)
Ending balance		(5,600.5)		(6,108.7)		(5,600.5)	(6,108.7)
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(5,687.5)		(5,437.5)		(5,729.2)	(5,718.6)
Reclassification due to adoption of new accounting standard								(105.2)
Ending balance		(5,600.5)		(6,108.7)		(5,600.5)	(6,108.7)
AOCI Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance						11.0	23.7
Reclassification due to adoption of new accounting standard								(23.7)
Continuing Operations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net other comprehensive income (loss)		87.0		(511.0)		82.9	(215.4)
Continuing Operations | Foreign Currency Translation Gains (Losses)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(1,601.4)		(900.2)		(1,569.7)	(1,191.7)
Reclassification due to adoption of new accounting standard								0.0
Other comprehensive income (loss) before reclassifications		31.4		(661.3)		(0.3)	(369.8)
Net amount reclassified from accumulated other comprehensive loss		0.0		0.0		0.0	0.0
Net other comprehensive income (loss)		31.4		(661.3)		(0.3)	(369.8)
Ending balance		(1,570.0)		(1,561.5)		(1,570.0)	(1,561.5)
Continuing Operations | Unrealized Net Gains (Losses) on Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(3.6)		(51.0)		(22.1)	113.5
Reclassification due to adoption of new accounting standard								(128.9)
Other comprehensive income (loss) before reclassifications		8.4		65.9		25.2	29.9
Net amount reclassified from accumulated other comprehensive loss		(0.3)		(33.0)		1.4	(32.6)
Net other comprehensive income (loss)		8.1		32.9		26.6	(2.7)
Ending balance		4.5		(18.1)		4.5	(18.1)
Continuing Operations | Defined Benefit Pension and Retiree Health Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(3,813.7)		(4,274.4)		(3,852.7)	(4,311.3)
Reclassification due to adoption of new accounting standard								0.0
Other comprehensive income (loss) before reclassifications		3.4		55.8		(2.3)	35.0
Net amount reclassified from accumulated other comprehensive loss		47.0		58.6		91.7	116.3
Net other comprehensive income (loss)		50.4		114.4		89.4	151.3
Ending balance		(3,763.3)		(4,160.0)		(3,763.3)	(4,160.0)
Continuing Operations | Effective Portion of Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(268.8)		(231.5)		(238.9)	(234.3)
Reclassification due to adoption of new accounting standard								0.0
Other comprehensive income (loss) before reclassifications		(6.1)		0.1		(39.0)	0.0
Net amount reclassified from accumulated other comprehensive loss		3.2		2.9		6.2	5.8
Net other comprehensive income (loss)		(2.9)		3.0		(32.8)	5.8
Ending balance		(271.7)		(228.5)		(271.7)	(228.5)
Discontinued Operations
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net other comprehensive income (loss)	[1]	0.0		(160.2)		56.8	(69.5)
Discontinued Operations | Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		0.0		19.6		(56.8)	(71.1)
Reclassification due to adoption of new accounting standard								$ 0.0
Other comprehensive income (loss) before reclassifications		0.0		(160.9)		(27.2)	(70.9)
Net amount reclassified from accumulated other comprehensive loss		0.0		0.7		84.0	1.4
Net other comprehensive income (loss)		0.0		(160.2)		56.8	(69.5)
Ending balance		0.0		$ (140.6)		0.0	$ (140.6)
Discontinued Operations | AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		45.8				45.8
Discontinued Operations | AOCI Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		$ 11.0				$ 11.0

[1] ⁽¹⁾ For the six months ended June 30, 2019, other comprehensive income related to discontinued operations consisted of $45.8 million of accumulated other comprehensive income attributable to controlling interest and $11.0 million of accumulated other comprehensive income attributable to noncontrolling interest.