Fair Value (Schedule Of Assets With Fair Value Changes On Nonrecurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Principal amount of other real estate owned property sold	$ 6	$ 13
Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	9	52
Gains (losses) from fair value changes	(5)	(36)
Private equity investments, carried at cost [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	1	1
Gains (losses) from fair value changes	(1)	(1)
Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	1
Gains (losses) from fair value changes	0	(2)
Nonrecurring Fair Value Measurements Asset Totals [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	10	54
Total gains (losses) from fair value changes measured on nonrecurring basis [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gains (losses) from fair value changes	(6)	(39)
Level 1 [Member] | Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Level 1 [Member] | Private equity investments, carried at cost [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Level 1 [Member] | Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Level 1 [Member] | Nonrecurring Fair Value Measurements Asset Totals [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Level 2 [Member] | Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	9	52
Level 2 [Member] | Private equity investments, carried at cost [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Level 2 [Member] | Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	1
Level 2 [Member] | Nonrecurring Fair Value Measurements Asset Totals [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	9	53
Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Fair Value, Inputs, Level 3 [Member] | Private equity investments, carried at cost [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	1	1
Fair Value, Inputs, Level 3 [Member] | Other Real Estate Owned [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	0	0
Fair Value, Inputs, Level 3 [Member] | Nonrecurring Fair Value Measurements Asset Totals [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of assets measured on nonrecurring basis	$ 1	$ 1