Goodwill and Other Intangible Assets - Gross Carrying Amount, Accumulated Amortization and Net Carrying Amount of Other Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 3,920	$ 3,938
Accumulated amortization	(2,711)	(2,618)
Net carrying amount	1,209	1,320	$ 1,544
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	2,734	2,761
Accumulated amortization	(1,868)	(1,808)
Net carrying amount	866	953
Technology
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	404	402
Accumulated amortization	(235)	(216)
Net carrying amount	169	186
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	684	690
Accumulated amortization	(528)	(516)
Net carrying amount	156	174
Other
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	98	85
Accumulated amortization	(80)	(78)
Net carrying amount	$ 18	$ 7