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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	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 30,353	$ 31,367
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(4,125)	(3,435)
Available-for-sale debt securities, net carrying value	26,228	27,933
Debt securities available for sale	26,228	27,933
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities held to maturity, amortized cost	772	812
Held To Maturity Debt Securities Gross Unrealized Gains	0	0
Held To Maturity Debt Securities Gross Unrealized Losses	(9)	(11)
Debt Securities held to maturity	763	801
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Loss	(60)	(50)
Debt Securities held to maturity, estimated fair value	703	751
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,316	1,310
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(130)	(123)
Available-for-sale debt securities, net carrying value	1,186	1,187
Debt securities available for sale	1,186	1,187
Federal agency securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,087	898
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(83)	(62)
Available-for-sale debt securities, net carrying value	1,004	836
Debt securities available for sale	1,004	836
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	18,802	19,477
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(3,062)	(2,523)
Available-for-sale debt securities, net carrying value	15,740	16,954
Debt securities available for sale	15,740	16,954
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities held to maturity, amortized cost	255	289
Held To Maturity Debt Securities Gross Unrealized Gains	0	0
Held To Maturity Debt Securities Gross Unrealized Losses	(8)	(10)
Debt Securities held to maturity	247	279
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Loss	(28)	(21)
Debt Securities held to maturity, estimated fair value	219	258
Residential Non-Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		0
Available-for-sale debt securities, net carrying value		1
Debt securities available for sale		1
Commercial Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	7,934	8,262
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(776)	(649)
Available-for-sale debt securities, net carrying value	7,158	7,613
Debt securities available for sale	7,158	7,613
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities held to maturity, amortized cost	517	523
Held To Maturity Debt Securities Gross Unrealized Gains	0	0
Held To Maturity Debt Securities Gross Unrealized Losses	(1)	(1)
Debt Securities held to maturity	516	522
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Debt Securities, Accumulated Unrecognized Holding Loss	(32)	(29)
Debt Securities held to maturity, estimated fair value	484	493
Commercial Non Agency [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	93	198
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(15)	(12)
Available-for-sale debt securities, net carrying value	78	186
Debt securities available for sale	78	186
Corporate and other debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,119	1,219
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(59)	(66)
Available-for-sale debt securities, net carrying value	1,060	1,154
Debt securities available for sale	$ 1,060	$ 1,154

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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-5B

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-5

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