Derivative Financial Instruments (Derivative Instrument Gains and Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	$ (20.6)	$ 30.6	$ (26.3)	$ 13.3
Non-Qualifying Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	(20.6)	30.6	(26.3)	13.3
Non-Qualifying Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	0.5	0.0	2.7	(2.6)
Non-Qualifying Hedges [Member] | Interest Rate Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	0.1	0.0	0.2	0.4
Non-Qualifying Hedges [Member] | Foreign Currency Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	(20.8)	21.6	(27.8)	(12.3)
Non-Qualifying Hedges [Member] | Equity Warrants [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	0.2	0.0	0.1	(0.3)
Non-Qualifying Hedges [Member] | TRS [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	(0.4)	8.6	(1.3)	26.8
Non-Qualifying Hedges [Member] | Interest Rate Lock Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	0.0	0.1	0.1	0.1
Non-Qualifying Hedges [Member] | Forward Sale Commitments On Agency MBS [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	(0.2)	0.0	(0.3)	0.0
Non-Qualifying Hedges [Member] | Credit Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives-income statement impact	$ 0.0	$ 0.3	$ 0.0	$ 1.2