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								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for credit losses on lending-related commitments		$ 17	$ 24	$ 17	$ 16	$ 35	$ 16	$ 49	$ 148	$ 74	$ 248	$ 147
Lending-related commitments
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					$ 41				$ 45	41	45	41
Charge-offs on lending related commitments	[1]									0	(11)	(1)
Provision for credit losses on lending-related commitments										1	7	5
Balance at end of period		$ 42				$ 41				$ 42	$ 41	$ 45

[1] Charge-offs result from the sale of unfunded lending-related commitments.