Derivative Financial Instruments - Impact of Derivatives on Consolidated Statement of Income (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	$ 281	$ 282	$ 875	$ 744
Foreign exchange contracts \| Foreign exchange trading services revenue
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	274	230	786	645
Foreign exchange contracts \| Interest expense
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	38	82	163	195
Interest rate contracts
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(9)	2	3	11
Other derivative contracts \| Other fee revenue
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(6)	(10)	(10)	(13)
Other derivative contracts \| Compensation and employee benefits
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	$ (16)	$ (22)	$ (67)	$ (94)