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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Retirement Benefits [Abstract]
Total net periodic defined benefit plan credit	$ (67)	$ (114)	$ (195)	$ (342)
Total defined contribution plans	506	461	1,454	1,292
Total pension and OPEB cost included in noninterest expense	$ 439	$ 347	$ 1,259	$ 950