Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 3,951,562	$ 1,486,583
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	29,774	143,817
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,828,968	1,660,143
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	525,636	398,532
Debt Securities, Available-for-sale, Unrealized Loss Position	6,780,530	3,146,726
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	555,410	542,349
U.S. Treasury and agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	546,511	734,473
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,036	71,967
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	837,124	201,701
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	95,117	27,391
Debt Securities, Available-for-sale, Unrealized Loss Position	1,383,635	936,174
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	98,153	99,358
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	249,310	160,078
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,465	10,037
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	136,483	60,381
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	23,579	18,004
Debt Securities, Available-for-sale, Unrealized Loss Position	385,793	220,459
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	26,044	28,041
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,155,741	592,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24,273	61,813
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,855,361	1,398,061
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	406,940	353,137
Debt Securities, Available-for-sale, Unrealized Loss Position	5,011,102	1,990,093
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 431,213	$ 414,950