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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ (35)	$ 0	$ (66)	$ 17
Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	31	34	30	42
Provision for credit losses	(2)	(1)	(1)	(9)
Balance at end of period	$ 29	$ 33	$ 29	$ 33