Goodwill And Intangible Assets (Summary Of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Beginning Balance				$ 685.4					$ 685.4
Impairment	$ (255.6)	$ 0.0	$ 0.0	0.0	$ (354.2)	$ 0.0	$ 0.0	$ 0.0	(255.6)	$ (354.2)	$ 0.0
Ending Balance	369.9				685.4				369.9	685.4
Impairment adjustment									4.0	15.0
Commercial Banking
Goodwill [Roll Forward]
Beginning Balance				642.2				689.0	642.2	689.0
Impairment									(255.6)	(34.8)
Other activity										(12.0)
Transfers to Held for Sale									(65.1)
Foreign exchange translation									5.2
Ending Balance	326.7				642.2				326.7	642.2	689.0
Consumer Banking
Goodwill [Roll Forward]
Beginning Balance				43.2				374.2	43.2	374.2
Impairment									0.0	(319.4)
Other activity										(11.6)
Transfers to Held for Sale									0.0
Foreign exchange translation									0.0
Ending Balance	43.2				43.2				43.2	43.2	374.2
Non-Strategic Portfolios
Goodwill [Roll Forward]
Beginning Balance				$ 685.4				$ 1,063.2	685.4	1,063.2
Impairment									(255.6)	(354.2)
Other activity										(23.6)
Transfers to Held for Sale									(65.1)
Foreign exchange translation									5.2
Ending Balance	$ 369.9				$ 685.4				$ 369.9	$ 685.4	$ 1,063.2
Consumer Banking And Commercial Banking
Goodwill [Roll Forward]
Impairment adjustment			$ 23.2