Fair Value (Changes In Estimated Fair Value For Financial Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative liabilities — non qualifying
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (11.5)	$ (55.5)
Included in earnings	(2.6)	44.0
Included in comprehensive income	0.0	0.0
Impairment	0.0	0.0
Transfer from Securities- HTM	0.0
Sales, paydowns and adjustments	0.0
Ending balance	(14.1)	(11.5)
FDIC True-up liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(61.9)	(56.9)
Included in earnings	(3.2)	(5.0)
Included in comprehensive income	0.0	0.0
Impairment	0.0	0.0
Transfer from Securities- HTM	0.0
Sales, paydowns and adjustments	0.0
Ending balance	(65.1)	(61.9)
Consideration holdback liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(47.2)	(60.8)
Included in earnings	1.2	(0.7)
Included in comprehensive income	0.0	0.0
Impairment	0.0	0.0
Transfer from Securities- HTM	0.0
Sales, paydowns and adjustments	0.0	14.3
Ending balance	(46.0)	(47.2)
Securities — AFS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	485.5	567.1
Included in earnings	6.6	(5.8)
Included in comprehensive income	7.7	20.6
Impairment	(1.1)	(3.3)
Transfer from Securities- HTM	66.8
Sales, paydowns and adjustments	(179.7)	(93.1)
Ending balance	385.8	485.5
Securities carried at fair value with changes recorded in net income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	283.5	339.7
Included in earnings	23.0	13.0
Included in comprehensive income	0.0	0.0
Impairment	0.0	0.0
Transfer from Securities- HTM	0.0
Sales, paydowns and adjustments	(306.1)	(69.2)
Ending balance	0.4	283.5
FDIC Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0.6	54.8
Included in earnings	0.8	10.7
Included in comprehensive income	0.0	0.0
Impairment	0.0	0.0
Transfer from Securities- HTM	0.0
Sales, paydowns and adjustments	(1.0)	(64.9)
Ending balance	0.4	0.6
Derivative assets — non qualifying
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0.0	0.0
Included in earnings	0.1	0.0
Included in comprehensive income	0.0	0.0
Impairment	0.0	0.0
Transfer from Securities- HTM	0.0
Sales, paydowns and adjustments	0.0	0.0
Ending balance	$ 0.1	$ 0.0