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, 2019	Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortization recognized on low income housing tax credit investments	$ 52	$ 152
Tax credits recognized on low income housing tax credit investments	54	165
Other tax benefits recognized on low income housing tax credit investments	$ 11	$ 35