Goodwill And Intangible Assets (Summary Of Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 182.3	$ 187.3
Accumulated Amortization	(69.3)	(46.6)
Net Carrying Amount	113.0	140.7	$ 166.1
Core deposit intangibles
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	126.3	126.3
Accumulated Amortization	(43.6)	(25.4)
Net Carrying Amount	82.7	100.9	118.8
Trade names
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	24.7	27.4
Accumulated Amortization	(7.7)	(6.1)
Net Carrying Amount	17.0	21.3	24.4
Customer relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	23.9	23.9
Accumulated Amortization	(10.6)	(7.1)
Net Carrying Amount	13.3	16.8	20.7
Other
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	7.4	9.7
Accumulated Amortization	(7.4)	(8.0)
Net Carrying Amount	$ 0.0	$ 1.7	$ 2.2