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
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses	$ 411	$ (13)
Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance at beginning of period	31	30
Provision for credit losses	(31)	0
Balance at end of period	$ 62	$ 30