Derivative Instruments And Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 13.0
Fair values of derivative assets reduced (increased) by net credit valuation adjustments	11.0	$ 3.0
Cash collateral pledged for derivative liabilities	106.0
Receive-fixed interest rate swaps	3,600.0
Additional collateral that would be required to be pledge if credit rating was downgraded by one notch	2.0
Gains deferred from terminated interest rate floors	23.5
Gains deferred from active receive-fixed interest rate swaps	18.4
Notional amount of received-fixed interest swaps added	2,000.0
Interest Rate Floors, Notional Amount	7,000.0
Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	5,088.0	1,187.0
Interest Rate Swaps [Member] | Fair Value Hedging [Member] | Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,500.0	500.0
Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	167.0	76.0
Other Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Gross amounts recognized	19.0	$ 39.0
Derivative Liability, Fair Value, Gross Liability	$ 167.0