Variable Interest Entities Affordable Housing Tax Credit Investments (Details) - Variable Interest Entity, Not Primary Beneficiary [Member] - Low Income Housing Tax Credit Investments [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Affordable housing tax credit investments included in other assets	$ 1,021	$ 1,144
Unfunded affordable housing tax credit commitments included in other liabilities	289	348
Loans and letters of credit commitments	329	317
Funded portion of loans and letters of credit commitments	$ 166	$ 129