Fair Value (Schedule Of Carrying Values And Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity, fair value	$ 850,473	$ 552,088
Loans and Leases Receivable, Net Amount	42,081,743	40,043,494
Time deposits	2,756,810	2,130,680
Long-term debt (less fair value hedges)	534,850	812,366
Fair Value, Inputs, Level 2 [Member] | Carrying Value [Member]
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Held-to-maturity, fair value	867,904	545,648
Time deposits	2,756,810	2,130,680
Foreign deposits	0	294,391
Other Short-term Borrowings	500,000	0
Long-term debt (less fair value hedges)	534,850	812,366
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	850,473	552,088
Time deposits	2,743,885	2,129,742
Foreign deposits	0	294,321
Other Short-term Borrowings	500,000	0
Long-term debt (less fair value hedges)	551,881	838,796
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	42,253,677	40,193,374
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	$ 42,110,544	$ 39,535,365