Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,672,996	$ 249,015
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	36,836	792
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	42,366	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,070	0
Debt Securities, Available-for-sale, Unrealized Loss Position	1,715,362	249,015
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	38,906	792
U.S. Treasury and agencies
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	119,093	29,493
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,773	312
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	18,805	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,023	0
Debt Securities, Available-for-sale, Unrealized Loss Position	137,898	29,493
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	2,796	312
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	53,099	4,357
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	717	31
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	53,099	4,357
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	717	31
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	1,500,804	215,165
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	34,346	449
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	23,561	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,047	0
Debt Securities, Available-for-sale, Unrealized Loss Position	1,524,365	215,165
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 35,393	$ 449

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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