Credit Quality And Allowance For Credit Losses (Troubled Debt Restructurings By Type Of Modification) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		$ 5	$ 61	$ 39	$ 170
Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	60	36	167
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		1	22	32	126
Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		1	2	1	2
Business loans | Real estate mortgage | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		1	36	3	39
Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1]	0	36	0	36
Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	1	0	3	3
Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	2	1	3	3
Principal Deferrals
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		64	174	64	174
Recorded balance of troubled debt restructuring modified during the period	[4]	3	61	36	137
Principal Deferrals | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		63	173	63	173
Recorded balance of troubled debt restructuring modified during the period	[4]	3	60	36	136
Principal Deferrals | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		59	127	59	127
Recorded balance of troubled debt restructuring modified during the period	[4]	1	22	32	95
Principal Deferrals | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		1	2	1	2
Recorded balance of troubled debt restructuring modified during the period	[4]	1	2	1	2
Principal Deferrals | Business loans | Real estate mortgage | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		3	44	3	44
Recorded balance of troubled debt restructuring modified during the period	[4]	1	36	3	39
Principal Deferrals | Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	[1]	0	37	0	37
Recorded balance of troubled debt restructuring modified during the period	[1],[4]	0	36	0	36
Principal Deferrals | Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	[2]	3	7	3	7
Recorded balance of troubled debt restructuring modified during the period	[2],[4]	1	0	3	3
Principal Deferrals | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	[3]	1	1	1	1
Recorded balance of troubled debt restructuring modified during the period	[3],[4]	0	1	0	1
Interest Rate Reductions
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		3	2	3	2
Recorded balance of troubled debt restructuring modified during the period		2	0	3	2
Interest Rate Reductions | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		0	0	0	0
Recorded balance of troubled debt restructuring modified during the period		0	0	0	0
Interest Rate Reductions | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		0	0	0	0
Recorded balance of troubled debt restructuring modified during the period		0	0	0	0
Interest Rate Reductions | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		0	0	0	0
Recorded balance of troubled debt restructuring modified during the period		0	0	0	0
Interest Rate Reductions | Business loans | Real estate mortgage | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		0	0	0	0
Recorded balance of troubled debt restructuring modified during the period		0	0	0	0
Interest Rate Reductions | Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	[1]	0	0	0	0
Recorded balance of troubled debt restructuring modified during the period	[1]	0	0	0	0
Interest Rate Reductions | Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	[2]	0	0	0	0
Recorded balance of troubled debt restructuring modified during the period	[2]	0	0	0	0
Interest Rate Reductions | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment	[3]	3	2	3	2
Recorded balance of troubled debt restructuring modified during the period	[3]	2	0	3	2
AB Note Restructures
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 0	31	$ 0	31
Recorded balance of troubled debt restructuring modified during the period	[5]		0		31
AB Note Restructures | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[5]		0		31
AB Note Restructures | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[5]		0		31
AB Note Restructures | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period			0		0
AB Note Restructures | Business loans | Real estate mortgage | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period			0		0
AB Note Restructures | Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1],[5]		0		0
AB Note Restructures | Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2],[5]		0		0
AB Note Restructures | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3],[5]		$ 0		$ 0

[1] Primarily loans to real estate developers.

[2] Primarily loans secured by owner-occupied real estate.

[3] Includes bankruptcy loans for which the court has discharged the borrower's obligation and the borrower has not reaffirmed the debt.

[4] Primarily represents loan balances where terms were extended 90 days or more at or above contractual interest rates.

[5] Loan restructurings whereby the original loan is restructured into two notes: an "A" note, which generally reflects the portion of the modified loan which is expected to be collected; and a "B" note, which is generally fully charged off.