Accumulated Other Comprehensive Income (Loss) (Details of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
After Tax
Other Comprehensive Income (Loss)	$ 18.0	$ 88.8
Other Unrealized Gains (Losses) on Securities Available for Sale
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	30.9	120.5
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(11.7)	(45.6)
After Tax
Other comprehensive income (loss), before reclassification, after tax	19.2	74.9
Net Unrealized Gains (Losses) on Securities Available for Sale
Before Tax
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.2	(0.3)
Net Change	31.1	120.2
Tax Effect
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.1)	0.1
Net Change	(11.8)	(45.5)
After Tax
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.1	(0.2)
Other Comprehensive Income (Loss)	19.3	74.7
Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	8.7	9.4
Reclassification Adjustment for (Gains) Losses Included in Net Income	(5.1)	0.6
Net Change	3.6	10.0
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(10.8)	(3.7)
Reclassification Adjustment for (Gains) Losses Included in Net Income	1.9	(0.2)
Net Change	(8.9)	(3.9)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(2.1)	5.7
Reclassification Adjustment for (Gains) Losses Included in Net Income	(3.2)	0.4
Other Comprehensive Income (Loss)	(5.3)	6.1
Net Foreign Currency Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	22.4	17.3
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.0	0.0
Net Change	(8.1)	(5.0)
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	(1.5)	(0.3)
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.0	0.0
Net Change	10.1	8.9
After Tax
Other comprehensive income (loss), before reclassification, after tax	20.9	17.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.0	0.0
Other Comprehensive Income (Loss)	2.0	3.9
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	0.0	4.2
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0.0	(1.0)
After Tax
Other comprehensive income (loss), before reclassification, after tax	0.0	3.2
Net Investment Hedge Gains (Losses)
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(30.5)	(26.5)
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	11.6	10.2
After Tax
Other comprehensive income (loss), before reclassification, after tax	(18.9)	(16.3)
Net Pension and Other Postretirement Benefit Adjustments
Before Tax
Other comprehensive income (loss), before reclassifications, before tax	(2.3)	0.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	6.4	6.4
Net Change	4.1	6.4
Tax Effect
Other comprehensive income (loss), before reclassifications, tax	0.0	0.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	(2.1)	(2.3)
Net Change	(2.1)	(2.3)
After Tax
Other comprehensive income (loss), before reclassification, after tax	(2.3)	0.0
Reclassification Adjustment for (Gains) Losses Included in Net Income	4.3	4.1
Other Comprehensive Income (Loss)	$ 2.0	$ 4.1