Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 313,726	$ 1,486,583
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7,021	143,817
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,811,915	1,660,143
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	483,755	398,532
Debt Securities, Available-for-sale, Unrealized Loss Position	3,125,641	3,146,726
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	490,776	542,349
U.S. Treasury and agencies
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	78,917	734,473
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,513	71,967
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	770,126	201,701
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	82,545	27,391
Debt Securities, Available-for-sale, Unrealized Loss Position	849,043	936,174
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	86,058	99,358
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	59,926	160,078
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	425	10,037
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	129,513	60,381
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	21,699	18,004
Debt Securities, Available-for-sale, Unrealized Loss Position	189,439	220,459
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	22,124	28,041
Mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	174,883	592,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,083	61,813
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,912,276	1,398,061
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	379,511	353,137
Debt Securities, Available-for-sale, Unrealized Loss Position	2,087,159	1,990,093
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 382,594	$ 414,950