Credit Quality And Allowance For Credit Losses (Troubled Debt Restructurings By Type Of Modification) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		$ 179	$ 34
Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		176	28
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		160	22
Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	0
Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		14	6
Business loans | Real estate | 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]	8	0
Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	6	6
Retail loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	6
Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	5
Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	1
Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		3	4
Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	1
Principal deferrals
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	$ 177	$ 31
Minimum period loan terms were extended		90 days	90 days
Principal deferrals | Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	$ 176	$ 28
Principal deferrals | Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	160	22
Principal deferrals | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	2	0
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	14	6
Principal deferrals | Business loans | Real estate | 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],[3]	8	0
Principal deferrals | Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2],[3]	6	6
Principal deferrals | Retail loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	1	3
Principal deferrals | Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	1	2
Principal deferrals | Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	0	1	[4]
Principal deferrals | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3],[4]	1	1
Principal deferrals | Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[3]	0	1	[4]
Interest rate reductions
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Business loans | Commercial borrower
Financing Receivable, Modifications [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, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Real estate | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Business loans | Real estate | 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	0
Interest rate reductions | Business loans | Real estate | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period	[2]	0	0
Interest rate reductions | Retail loans
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Retail loans | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Retail loans | Real estate
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		0	0
Interest rate reductions | Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		2	3
Interest rate reductions | Retail loans | Other consumer | Consumer borrower
Financing Receivable, Modifications [Line Items]
Recorded balance of troubled debt restructuring modified during the period		$ 0	$ 0

[1] Primarily loans to real estate developers.

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

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

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