Investment Securities - Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Less than 12 months	$ 320	$ 300
12 months or longer	7,615	7,699
Total fair value	7,935	7,999
Unrealized Losses
Less than 12 months	(5)	(4)
12 months or longer	(1,176)	(1,108)
Total unrealized losses	(1,181)	(1,112)
Government agency issued MBS
Schedule of Investments [Line Items]
Less than 12 months	59	140
12 months or longer	4,224	4,231
Total fair value	4,283	4,371
Unrealized Losses
Less than 12 months	(1)	(2)
12 months or longer	(621)	(577)
Total unrealized losses	(622)	(579)
Government agency issued CMO
Schedule of Investments [Line Items]
Less than 12 months	11	32
12 months or longer	2,057	2,098
Total fair value	2,068	2,130
Unrealized Losses
Less than 12 months	0	0
12 months or longer	(350)	(341)
Total unrealized losses	(350)	(341)
Other U.S. government agencies
Schedule of Investments [Line Items]
Less than 12 months	216	114
12 months or longer	874	905
Total fair value	1,090	1,019
Unrealized Losses
Less than 12 months	(4)	(2)
12 months or longer	(158)	(149)
Total unrealized losses	(162)	(151)
States and municipalities
Schedule of Investments [Line Items]
Less than 12 months	34	14
12 months or longer	460	465
Total fair value	494	479
Unrealized Losses
Less than 12 months	0	0
12 months or longer	(47)	(41)
Total unrealized losses	$ (47)	$ (41)