Loan Sale and Servicing Activities and Variable Interest Entities (Narrative) (Details) - Cumulative effect of adopting ASU 2014-01 [Member] - Low Income Housing Tax Credit Investments [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Amortization Recognized Low Income Housing Tax Credit Investments	$ 58	$ 200
Tax Credits Recognized Low Income Housing Tax Credit Investments	60	200
Other Tax Benefits Recognized Low Income Housing Tax Credit Investments	$ 21	$ 100