Credit Quality And Allowance For Credit Losses Credit Quality And Allowance For Credit Losses (Troubled Debt Restructuring Subsequent Default) (Details) - Principal deferrals - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Balance		$ 118	$ 147
Subsequent default during period		3	14
Business loans | Commercial borrower
Financing Receivable, Modifications [Line Items]
Balance		117	145
Subsequent default during period		3	14
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Balance		77	140
Subsequent default during period			13
Business loans | Commercial borrower | International loans
Financing Receivable, Modifications [Line Items]
Balance		0	0
Subsequent default during period		0	0
Business loans | Real estate mortgage | Commercial borrower | Domestic loans
Financing Receivable, Modifications [Line Items]
Balance		40	5
Subsequent default during period		0	1
Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Modifications [Line Items]
Balance	[1]	37	0
Subsequent default during period	[1]	0	0
Business loans | Real estate mortgage | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Modifications [Line Items]
Balance	[2]	3	5
Subsequent default during period		0	1	[2]
Retail loans | Home equity | Consumer borrower
Financing Receivable, Modifications [Line Items]
Balance	[3]	1	2
Subsequent default during period		$ 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.