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] $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortization recognized on low income housing tax credit investments	$ 55
Tax credits recognized on low income housing tax credit investments	57
Other tax benefits recognized on low income housing tax credit investments	$ 13