Pension and Other Postretirement Employee Benefit Plans - Net Periodic Benefit Costs and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Retirement Benefits [Abstract]
Total net periodic defined benefit plan cost/(credit)	$ (115)	$ (94)	$ (228)	$ (188)
Total defined contribution plans	443	397	831	762
Total pension and OPEB cost included in noninterest expense	$ 328	$ 303	$ 603	$ 574