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		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance		$ 35	$ 29
Subsequent default during period		10	0
Business loans | Commercial borrower
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance		35	28
Business loans | Commercial borrower | Domestic loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance		33	26
Business loans | Commercial mortgage | Commercial borrower | Domestic loans | Other business lines
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance	[1]	2	2
Retail loans | Home equity | Consumer borrower | Domestic loans | Commercial Real Estate business line
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance	[2]	$ 0	$ 1

[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.