Variable Interest Entities And Preferred Securities Of Subsidiaries Variable Interest Entities and Preferred Securities of Subsidiaries (Activity Between Entities Footnotes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entities And Preferred Securities Of Subsidiaries [Abstract]
Accretion Income for Amortization of Purchase Accounting Adjustment, Financial Assets	$ 19	$ 19	$ 19
Accretion Expense for Amortization of Purchase Accounting Adjustment, Financial Liabiities	$ 7	$ 7	$ 7