Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Balance	$ 26,128.9	$ 25,965.3
Other comprehensive income (loss), net of tax	(29.6)	(4.5)
Balance	26,567.7	26,186.5
Investment Securities [Member]
Balance	0.8	0.1
Other comprehensive income (loss) before reclassifications and income tax benefit (expense)	(0.6)	0.8
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Income tax benefit (expense)	0.2	(0.2)
Other comprehensive income (loss), net of tax	(0.4)	0.6
Balance	0.4	0.7
Defined Benefit Plans [Member]
Balance	(55.1)	(53.8)
Other comprehensive income (loss) before reclassifications and income tax benefit (expense)	(2.0)	(2.7)
Amounts reclassified from accumulated other comprehensive income (loss)	1.2	1.2
Income tax benefit (expense)	0.2	0.4
Other comprehensive income (loss), net of tax	(0.6)	(1.1)
Balance	(55.7)	(54.9)
Derivative Investments [Member]
Balance	69.0	69.7
Other comprehensive income (loss) before reclassifications and income tax benefit (expense)	0.0	0.3
Amounts reclassified from accumulated other comprehensive income (loss)	(1.8)	(0.3)
Income tax benefit (expense)	0.4	0.0
Other comprehensive income (loss), net of tax	(1.4)	0.0
Balance	67.6	69.7
Foreign Currency Translation [Member]
Balance	(11.3)	(10.7)
Other comprehensive income (loss) before reclassifications and income tax benefit (expense)	(27.8)	(4.0)
Amounts reclassified from accumulated other comprehensive income (loss)	0.6	0.0
Income tax benefit (expense)	0.0	0.0
Other comprehensive income (loss), net of tax	(27.2)	(4.0)
Balance	(38.5)	(14.7)
Accumulated Other Comprehensive Income (Loss) [Member]
Balance	3.4	5.3
Other comprehensive income (loss) before reclassifications and income tax benefit (expense)	(30.4)	(5.6)
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.9
Income tax benefit (expense)	0.8	0.2
Other comprehensive income (loss), net of tax	(29.6)	(4.5)
Balance	$ (26.2)	$ 0.8