Fair Value Measurements (Estimated Fair Values Of Financial Instruments Not Recorded At Fair Value In Their Entirety On A Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Cash and due from banks		$ 945	$ 1,438
Interest-bearing deposits with banks		4,894	4,407
Investment securities held-to-maturity		0	1,266
Total loans, net of allowance for loan losses		48,346	48,461
Demand deposits (noninterest-bearing)		29,301	32,071
Customer certificates of deposit		2,051	2,165
Total deposits		56,006	57,903
Short-term borrowings		84	10
Medium- and long-term debt		6,418	4,622
Carrying Amount
Cash and due from banks		945	1,438
Interest-bearing deposits with banks		4,894	4,407
Investment securities held-to-maturity			1,266
Loans held-for-sale		2	4
Total loans, net of allowance for loan losses	[1]	48,346	48,461
Customers' liability on acceptances outstanding		4	2
Restricted equity investments		248	207
Nonmarketable equity securities	[2]	6	6
Demand deposits (noninterest-bearing)		29,301	32,071
Interest-bearing deposits		24,654	23,667
Customer certificates of deposit		2,051	2,165
Total deposits		56,006	57,903
Short-term borrowings		84	10
Acceptances outstanding		4	2
Medium- and long-term debt		6,418	4,622
Credit-related financial instruments		(57)	(67)
Estimated Fair Value
Cash and due from banks		945	1,438
Interest-bearing deposits with banks		4,894	4,407
Investment securities held-to-maturity			1,246
Loans held-for-sale		2	4
Total loans, net of allowance for loan losses	[1]	48,352	48,153
Customers' liability on acceptances outstanding		4	2
Restricted equity investments		248	207
Nonmarketable equity securities	[2]	11	9
Demand deposits (noninterest-bearing)		29,301	32,071
Interest-bearing deposits		24,654	23,667
Customer certificates of deposit		2,013	2,142
Total deposits		55,968	57,880
Short-term borrowings		84	10
Acceptances outstanding		4	2
Medium- and long-term debt		6,431	4,636
Credit-related financial instruments		(57)	(67)
Level 1 | Estimated Fair Value
Cash and due from banks		945	1,438
Interest-bearing deposits with banks		4,894	4,407
Investment securities held-to-maturity			0
Loans held-for-sale		0	0
Total loans, net of allowance for loan losses	[1]	0	0
Customers' liability on acceptances outstanding		4	2
Restricted equity investments		248	207
Demand deposits (noninterest-bearing)		0	0
Interest-bearing deposits		0	0
Customer certificates of deposit		0	0
Total deposits		0	0
Short-term borrowings		84	10
Acceptances outstanding		4	2
Medium- and long-term debt		0	0
Credit-related financial instruments		0	0
Level 2 | Estimated Fair Value
Cash and due from banks		0	0
Interest-bearing deposits with banks		0	0
Investment securities held-to-maturity			1,246
Loans held-for-sale		2	4
Total loans, net of allowance for loan losses	[1]	0	0
Customers' liability on acceptances outstanding		0	0
Restricted equity investments		0	0
Demand deposits (noninterest-bearing)		29,301	32,071
Interest-bearing deposits		24,654	23,667
Customer certificates of deposit		2,013	2,142
Total deposits		55,968	57,880
Short-term borrowings		0	0
Acceptances outstanding		0	0
Medium- and long-term debt		6,431	4,636
Credit-related financial instruments		0	0
Level 3 | Estimated Fair Value
Cash and due from banks		0	0
Interest-bearing deposits with banks		0	0
Investment securities held-to-maturity			0
Loans held-for-sale		0	0
Total loans, net of allowance for loan losses	[1]	48,352	48,153
Customers' liability on acceptances outstanding		0	0
Restricted equity investments		0	0
Demand deposits (noninterest-bearing)		0	0
Interest-bearing deposits		0	0
Customer certificates of deposit		0	0
Total deposits		0	0
Short-term borrowings		0	0
Acceptances outstanding		0	0
Medium- and long-term debt		0	0
Credit-related financial instruments		(57)	(67)
Nonrecurring
Total loans, net of allowance for loan losses		$ 58	$ 116

[1] Included $58 million and $116 million of impaired loans recorded at fair value on a nonrecurring basis at September 30, 2018 and December 31, 2017, respectively.

[2] Certain investments that are measured at fair value using the net asset value have not been classified in the fair value hierarchy. The fair value amounts presented in the table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the Consolidated Balance Sheets.