Credit Quality And Allowance For Credit Losses (Changes In The Allowance For Credit Losses On Lending-Related Commitments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for credit losses	$ 0	$ 24	$ (17)	$ 57
Lending-related commitments
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	34	48	42	41
Provision for credit losses	(1)	(7)	(9)	0
Balance at end of period	$ 33	$ 41	$ 33	$ 41