Derivative Financial Instruments And Hedging Activities (Schedule Of Gains (Losses) Recognized Related To Derivatives Not Designated As Hedging Instruments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	$ 183	$ 117	$ 35
Mortgage Income [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	111	72	(20)
Mortgage Income [Member] \| Interest Rate Swaps [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	83	68	(12)
Mortgage Income [Member] \| Interest Rate Options [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	30	(1)	0
Mortgage Income [Member] \| Interest Rate Futures And Forward Commitments [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	(2)	5	(8)
Capital markets income [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	72	45	55
Capital markets income [Member] \| Interest Rate Swaps [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	21	13	19
Capital markets income [Member] \| Interest Rate Options [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	36	23	28
Capital markets income [Member] \| Interest Rate Futures And Forward Commitments [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	14	10	3
Capital markets income [Member] \| Other Contracts [Member] \| Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gain or (Loss) of Derivatives Not Designated as Hedging Instruments	$ 1	$ (1)	$ 5