Loan Sale and Servicing Activities and Variable Interest Entities Loan Sale and Servicing Activities and Variable Interest Entities (Additional Information) (Details) - Low Income Housing Tax Credit Investments [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other tax benefits recognized on low income housing tax credit investments	$ 10	$ 32
New Accounting Pronouncement, Early Adoption, Effect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortization recognized on low income housing tax credit investments	44	140
Tax credits recognized on low income housing tax credit investments	$ 46	$ 144

Loan Sale and Servicing Activities and Variable Interest Entities Loan Sale and Servicing Activities and Variable Interest Entities (Additional Information) (Details) - Low Income Housing Tax Credit Investments [Member] - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Sep. 30, 2020

Accounts, Notes, Loans and Financing Receivable [Line Items]

Other tax benefits recognized on low income housing tax credit investments

$ 10

$ 32

New Accounting Pronouncement, Early Adoption, Effect [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Amortization recognized on low income housing tax credit investments

140

Tax credits recognized on low income housing tax credit investments

$ 46

$ 144