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	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortization recognized on low income housing tax credit investments	$ 45	$ 100
Tax credits recognized on low income housing tax credit investments	54	111
Other tax benefits recognized on low income housing tax credit investments	$ 11	$ 24