Pension and Other Postretirement Employee Benefit Plans - Net Periodic Benefit Costs and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Retirement Benefits [Abstract]
Total net periodic defined benefit plan cost/(credit)	$ (114)	$ (104)	$ (342)	$ (292)
Total defined contribution plans	461	403	1,292	1,165
Total pension and OPEB cost included in noninterest expense	$ 347	$ 299	$ 950	$ 873