Fair Value (Schedule Of Carrying Values And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity, fair value	$ 752
Long-term debt (less fair value hedges)	383	$ 383
Fair Value, Inputs, Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Loans and leases (including loans held for sale), net of allowance	44,700	44,306
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Loans and leases (including loans held for sale), net of allowance	43,802	44,226
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity Securities	768	770
Time deposits	3,581	3,115
Other Short-term Borrowings	4,450	3,600
Long-term debt (less fair value hedges)	383	383
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity, fair value	752	762
Time deposits	3,554	3,099
Other Short-term Borrowings	4,450	3,600
Long-term debt (less fair value hedges)	$ 384	$ 402