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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
After Tax
Other Comprehensive Income	$ 3.8	$ (20.1)	$ 34.9	$ 113.0
Unrealized Gains (Losses) on Securities Available for Sale
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(3.4)	(22.3)	29.6	152.2
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	1.0	8.4	(11.5)	(57.6)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(2.4)	(13.9)	18.1	94.6
Net Unrealized Gains (Losses) on Securities Available for Sale
Before Tax
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.4	(0.2)	1.0	(0.5)
Net Change	(3.0)	(22.5)	30.6	151.7
Tax Effect
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.2)	0.2	(0.4)	0.2
Net Change	0.8	8.6	(11.9)	(57.4)
After Tax
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.2	0.0	0.6	(0.3)
Other Comprehensive Income	(2.2)	(13.9)	18.7	94.3
Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	2.9	(6.3)	20.6	3.7
Reclassification Adjustment for (Gains) Losses Included in Net Income	(6.1)	4.6	(16.4)	5.2
Net Change	(3.2)	(1.7)	4.2	8.9
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(1.0)	3.5	(15.3)	(0.3)
Reclassification Adjustment for (Gains) Losses Included in Net Income	2.3	(1.7)	6.2	(2.0)
Net Change	1.3	1.8	(9.1)	(2.3)
After Tax
Other comprehensive income (loss), before reclassification, after tax	1.9	(2.8)	5.3	3.4
Reclassification Adjustment for (Gains) Losses Included in Net Income	(3.8)	2.9	(10.2)	3.2
Other Comprehensive Income	(1.9)	0.1	(4.9)	6.6
Net Foreign Currency Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	47.3	(11.7)	136.4	(52.7)
Net Change	(14.4)	(6.8)	(57.3)	36.9
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(6.0)	(0.9)	(6.1)	(2.3)
Net Change	18.0	(2.7)	67.8	(36.2)
After Tax
Other comprehensive income (loss), before reclassification, after tax	41.3	(12.6)	130.3	(55.0)
Other Comprehensive Income	3.6	(9.5)	10.5	0.7
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	0.6	0.8	1.0	2.0
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(0.2)	(0.3)	(0.4)	(0.8)
After Tax
Other comprehensive income (loss), before reclassification, after tax	0.4	0.5	0.6	1.2
Net Investment Hedge Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(62.3)	4.1	(194.7)	87.6
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	24.2	(1.5)	74.3	(33.1)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(38.1)	2.6	(120.4)	54.5
Net Pension and Other Postretirement Benefit Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(0.7)	0.0	(3.2)	0.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	7.4	6.3	20.6	19.1
Net Change	6.7	6.3	17.4	19.1
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0.2	0.0	0.3	0.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	(2.6)	(3.0)	(7.1)	(7.7)
Net Change	(2.4)	(3.0)	(6.8)	(7.7)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(0.5)	0.0	(2.9)	0.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	4.8	3.3	13.5	11.4
Other Comprehensive Income	$ 4.3	$ 3.3	$ 10.6	$ 11.4