Investment Securities - Schedule of Investments within the Available for Sale Portfolio that had Unrealized Losses (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Less than 12 months	$ 154	$ 300
12 months or longer	7,420	7,699
Total fair value	7,574	7,999
Unrealized Losses
Less than 12 months	0	(4)
12 months or longer	(897)	(1,108)
Total unrealized losses	(897)	(1,112)
Government agency issued MBS
Schedule of Investments [Line Items]
Less than 12 months	0	140
12 months or longer	4,057	4,231
Total fair value	4,057	4,371
Unrealized Losses
Less than 12 months	0	(2)
12 months or longer	(460)	(577)
Total unrealized losses	(460)	(579)
Government agency issued CMO
Schedule of Investments [Line Items]
Less than 12 months	150	32
12 months or longer	2,002	2,098
Total fair value	2,152	2,130
Unrealized Losses
Less than 12 months	0	0
12 months or longer	(276)	(341)
Total unrealized losses	(276)	(341)
Other U.S. government agencies
Schedule of Investments [Line Items]
Less than 12 months	0	114
12 months or longer	909	905
Total fair value	909	1,019
Unrealized Losses
Less than 12 months	0	(2)
12 months or longer	(122)	(149)
Total unrealized losses	(122)	(151)
States and municipalities
Schedule of Investments [Line Items]
Less than 12 months	4	14
12 months or longer	452	465
Total fair value	456	479
Unrealized Losses
Less than 12 months	0	0
12 months or longer	(39)	(41)
Total unrealized losses	$ (39)	$ (41)