Fair Value (Schedule Of Carrying Values And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity, fair value	$ 762
Loans and Leases Receivable, Net Amount	44,262	$ 42,082
Time deposits	3,115	2,757
Long-term debt (less fair value hedges)	383	535
Carrying Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Loans and Leases Receivable, Net Amount		42,254
Other Short-term Borrowings		500
Long-term debt (less fair value hedges)		535
Estimated Fair Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Loans and Leases Receivable, Net Amount		42,111
Time deposits		2,744
Other Short-term Borrowings		500
Long-term debt (less fair value hedges)		552
Fair Value, Inputs, Level 2 [Member] | Carrying Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity Securities	770	868
Time deposits	3,115
Other Short-term Borrowings	3,600
Long-term debt (less fair value hedges)	383
Fair Value, Inputs, Level 2 [Member] | Estimated Fair Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity, fair value	762	$ 850
Time deposits	3,099
Other Short-term Borrowings	3,600
Long-term debt (less fair value hedges)	402
Fair Value, Inputs, Level 3 [Member] | Carrying Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Loans and Leases Receivable, Net Amount	44,306
Fair Value, Inputs, Level 3 [Member] | Estimated Fair Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Loans and Leases Receivable, Net Amount	$ 44,226