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Business Segments - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
Business Segments - Narrative (Details) $ in Millions	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) segment	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information
Number of business segments \| segment			3
Other noninterest expense	$ (253)	$ (266)	$ (521)	$ (519)
Wealth and asset management revenue	(159)	(143)	(320)	(289)
Operating Segments \| Investment Advisors [Member]
Segment Reporting Information
Other noninterest expense	(38)	(35)	(74)	(71)
Wealth and asset management revenue	$ (96)	$ (89)	$ (197)	$ (182)
Operating Segments \| Investment Advisors [Member] \| Revision of Prior Period, Adjustment
Segment Reporting Information
Other noninterest expense					$ 186	$ 177	$ 180
Wealth and asset management revenue					$ 186	$ 177	$ 180