Credit Quality And Allowance For Credit Losses (Troubled Debt Restructurings By Type Of Modification) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		$ 29	$ 33
Business loans | Commercial borrower
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		28	30
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		28	27
Business loans | Commercial borrower | International loans | Other business lines
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	1
Business loans | Commercial borrower | Real estate mortgage | Domestic loans | Other business lines
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1]	0	2
Retail loans | Consumer borrower | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	1	3
Principal deferrals
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	$ 28	$ 30
Minimum period loan terms were extended		90 days	90 days
Principal deferrals | Business loans | Commercial borrower
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	$ 28	$ 30
Principal deferrals | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	28	27
Principal deferrals | Business loans | Commercial borrower | International loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	0	1
Principal deferrals | Business loans | Commercial borrower | Real estate mortgage | Domestic loans | Other business lines
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1],[3]	0	2
Principal deferrals | Retail loans | Consumer borrower | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2],[3]	0	0
Interest Rate Reductions
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		1	3
Interest Rate Reductions | Business loans | Commercial borrower
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest Rate Reductions | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest Rate Reductions | Business loans | Commercial borrower | International loans | Other business lines
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest Rate Reductions | Business loans | Commercial borrower | Real estate mortgage | Domestic loans | Other business lines
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[1]	0	0
Interest Rate Reductions | Retail loans | Consumer borrower | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	$ 1	$ 3

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

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

[3] Primarily represents loan balances where terms were extended 90 days or more at or above contractual interest rates. Also includes commercial loans restructured in bankruptcy.