Loans - Wholesale Loan Portfolio, Nonaccrual (Details) - Wholesale - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
With an allowance	$ 1,551	$ 2,818
Without an allowance	533	500
Total nonaccrual loans	2,084	3,318
Secured by real estate
Financing Receivable, Nonaccrual [Line Items]
With an allowance	309	351
Without an allowance	66	132
Total nonaccrual loans	375	483
Commercial and industrial
Financing Receivable, Nonaccrual [Line Items]
With an allowance	722	1,667
Without an allowance	272	264
Total nonaccrual loans	994	1,931
Other
Financing Receivable, Nonaccrual [Line Items]
With an allowance	520	800
Without an allowance	195	104
Total nonaccrual loans	$ 715	$ 904