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Debt Securities (Schedule Of Amortized Cost, Gross Unrealized Gains And Losses, And Estimated Fair Value Of Securities Available For Sale And Securities Held To Maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 30,909	$ 30,864
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	38	62
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(3,066)	(2,822)
Available-for-sale debt securities, net carrying value	27,881	28,104
Debt securities available for sale	27,881	28,104
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities held to maturity, amortized cost	751	763
Held To Maturity Debt Securities Gross Unrealized Gains	0	0
Held To Maturity Debt Securities Gross Unrealized Losses	(8)	(9)
Debt Securities held to maturity	743	754
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Loss	(42)	(38)
Debt Securities held to maturity, estimated fair value	701	716
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,211	1,322
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(101)	(99)
Available-for-sale debt securities, net carrying value	1,110	1,223
Debt securities available for sale	1,110	1,223
Federal agency securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	566	1,085
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(23)	(46)
Available-for-sale debt securities, net carrying value	545	1,043
Debt securities available for sale	545	1,043
US States and Political Subdivisions Debt Securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Available-for-sale debt securities, net carrying value	2	2
Debt securities available for sale	2	2
Residential Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	20,686	19,450
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	33	52
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(2,369)	(2,130)
Available-for-sale debt securities, net carrying value	18,350	17,372
Debt securities available for sale	18,350	17,372
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities held to maturity, amortized cost	237	247
Held To Maturity Debt Securities Gross Unrealized Gains	0	0
Held To Maturity Debt Securities Gross Unrealized Losses	(8)	(8)
Debt Securities held to maturity	229	239
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Loss	(18)	(16)
Debt Securities held to maturity, estimated fair value	211	223
Commercial Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,304	7,807
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(528)	(502)
Available-for-sale debt securities, net carrying value	6,777	7,307
Debt securities available for sale	6,777	7,307
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities held to maturity, amortized cost	514	516
Held To Maturity Debt Securities Gross Unrealized Gains	0	0
Held To Maturity Debt Securities Gross Unrealized Losses	0	(1)
Debt Securities held to maturity	514	515
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Loss	(24)	(22)
Debt Securities held to maturity, estimated fair value	490	493
Commercial Non Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	93	93
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(11)	(10)
Available-for-sale debt securities, net carrying value	82	83
Debt securities available for sale	82	83
Corporate and other debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,047	1,105
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(34)	(35)
Available-for-sale debt securities, net carrying value	1,015	1,074
Debt securities available for sale	$ 1,015	$ 1,074

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