Loans - Wholesale Loan Portfolio, Nonaccrual (Details) - Wholesale - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Nonaccrual [Line Items]
With an allowance	$ 2,818	$ 885
Without an allowance	500	172
Total nonaccrual loans	3,318	1,057
Secured by real estate
Financing Receivable, Nonaccrual [Line Items]
With an allowance	351	169
Without an allowance	132	14
Total nonaccrual loans	483	183
Commercial and industrial
Financing Receivable, Nonaccrual [Line Items]
With an allowance	1,667	688
Without an allowance	264	156
Total nonaccrual loans	1,931	844
Other
Financing Receivable, Nonaccrual [Line Items]
With an allowance	800	28
Without an allowance	104	2
Total nonaccrual loans	$ 904	$ 30