Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 249,015	$ 606,646
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	792	5,982
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	404,708
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	4,065
Debt Securities, Available-for-sale, Unrealized Loss Position	249,015	1,011,354
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	792	10,047
U.S. Treasury and agencies
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	29,493	313,169
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	312	4,324
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	29,493	313,169
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	312	4,324
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,357	4,611
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	31	30
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	1,906
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	7
Debt Securities, Available-for-sale, Unrealized Loss Position	4,357	6,517
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	31	37
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	215,165	288,866
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	449	1,628
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	402,802
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	4,058
Debt Securities, Available-for-sale, Unrealized Loss Position	215,165	691,668
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 449	$ 5,686

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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