Accumulated Other Comprehensive Income (Loss) (Details of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
After Tax
Other Comprehensive Income	$ (18.8)	$ 3.8	$ (87.3)	$ 34.9
Net Unrealized Gains (Losses) on Debt Securities Available for Sale
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(42.8)	(3.4)	(144.6)	29.6
Reclassification adjustment, before tax	0.0	0.4	0.0	1.0
Net Change	(42.8)	(3.0)	(144.6)	30.6
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	10.7	1.0	37.6	(11.5)
Reclassification adjustment, tax	0.0	(0.2)	0.0	(0.4)
Net Change	10.7	0.8	37.6	(11.9)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(32.1)	(2.4)	(107.0)	18.1
Reclassification adjustment, after tax	0.0	0.2	0.0	0.6
Other Comprehensive Income	(32.1)	(2.2)	(107.0)	18.7
Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax
Reclassification adjustment, before tax	(17.4)	(6.1)	(51.0)	(16.4)
Net Change	(5.7)	(3.2)	(15.4)	4.2
Tax Effect
Reclassification adjustment, tax	4.3	2.3	12.9	6.2
Net Change	1.5	1.3	4.0	(9.1)
After Tax
Reclassification adjustment, after tax	(13.1)	(3.8)	(38.1)	(10.2)
Other Comprehensive Income	(4.2)	(1.9)	(11.4)	(4.9)
Net Foreign Currency Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(16.6)	47.3	(77.5)	136.4
Net Change	19.8	(14.4)	41.7	(57.3)
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(0.4)	(6.0)	(0.9)	(6.1)
Net Change	(9.2)	18.0	(30.6)	67.8
After Tax
Other comprehensive income (loss), before reclassification, after tax	(17.0)	41.3	(78.4)	130.3
Other Comprehensive Income	10.6	3.6	11.1	10.5
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(1.1)	0.6	(1.7)	1.0
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0.2	(0.2)	0.4	(0.4)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(0.9)	0.4	(1.3)	0.6
Net Investment Hedge Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	37.5	(62.3)	120.9	(194.7)
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(9.0)	24.2	(30.1)	74.3
After Tax
Other comprehensive income (loss), before reclassification, after tax	28.5	(38.1)	90.8	(120.4)
Net Pension and Other Postretirement Benefit Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	0.0	(0.7)	10.1	(3.2)
Reclassification adjustment, before tax	9.2	7.4	27.8	20.6
Net Change	9.2	6.7	37.9	17.4
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0.0	0.2	(2.4)	0.3
Reclassification adjustment, tax	(2.3)	(2.6)	(15.5)	(7.1)
Net Change	(2.3)	(2.4)	(17.9)	(6.8)
After Tax
Other comprehensive income (loss), before reclassification, after tax	0.0	(0.5)	7.7	(2.9)
Reclassification adjustment, after tax	6.9	4.8	12.3	13.5
Other Comprehensive Income	6.9	4.3	20.0	10.6
Foreign Exchange Contracts | Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	11.6	3.1	36.9	19.4
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(2.8)	(1.1)	(9.2)	(14.8)
After Tax
Other comprehensive income (loss), before reclassification, after tax	8.8	2.0	27.7	4.6
Interest Rate Contracts | Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	0.1	(0.2)	(1.3)	1.2
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0.0	0.1	0.3	(0.5)
After Tax
Other comprehensive income (loss), before reclassification, after tax	$ 0.1	$ (0.1)	$ (1.0)	$ 0.7