Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	$ (135.2)	$ (240.4)
Balance, January 1, 2018	(149.3)	(219.8)
Other comprehensive income (loss), before reclassifications, net of tax	0.7	37.3
Amounts reclassified from accumulated other comprehensive income, net of tax	(14.8)	(16.7)
Other comprehensive income (loss), net of tax	(13.5)	20.6
Accumulated other comprehensive income (loss), net of tax ending balance	(149.3)	(219.8)
Other comprehensive income (loss), net of tax	(14.1)	20.6
Unrealized gains (losses) on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	4.2	(4.0)
Balance, January 1, 2018	(3.6)	2.9
Other comprehensive income (loss), before reclassifications, net of tax	(20.8)	7.1
Amounts reclassified from accumulated other comprehensive income, net of tax	13.0	(0.2)
Other comprehensive income (loss), net of tax	(7.8)	6.9
Accumulated other comprehensive income (loss), net of tax ending balance	(3.6)	2.9
Unrealized gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	7.8	34.7
Balance, January 1, 2018	41.6	51.6
Other comprehensive income (loss), before reclassifications, net of tax	60.7	31.2
Amounts reclassified from accumulated other comprehensive income, net of tax	(26.9)	(14.3)
Other comprehensive income (loss), net of tax	33.8	16.9
Accumulated other comprehensive income (loss), net of tax ending balance	41.6	51.6
Gains (losses) on net investment hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	25.1	3.5
Balance, January 1, 2018	48.1	17.5
Other comprehensive income (loss), before reclassifications, net of tax	23.9	16.2
Amounts reclassified from accumulated other comprehensive income, net of tax	(0.9)	(2.2)
Other comprehensive income (loss), net of tax	23.0	14.0
Accumulated other comprehensive income (loss), net of tax ending balance	48.1	17.5
Unfunded status of postretirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	(32.8)	(31.3)
Balance, January 1, 2018	(32.0)	(30.7)
Other comprehensive income (loss), before reclassifications, net of tax	0.8	0.6
Amounts reclassified from accumulated other comprehensive income, net of tax	0.0	0.0
Other comprehensive income (loss), net of tax	0.8	0.6
Accumulated other comprehensive income (loss), net of tax ending balance	(32.0)	(30.7)
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	(139.5)	(243.3)
Balance, January 1, 2018	(203.4)	(261.1)
Other comprehensive income (loss), before reclassifications, net of tax	(63.9)	(17.8)
Amounts reclassified from accumulated other comprehensive income, net of tax	0.0	0.0
Other comprehensive income (loss), net of tax	(63.9)	(17.8)
Accumulated other comprehensive income (loss), net of tax ending balance	$ (203.4)	$ (261.1)