Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,292,794	$ 1,486,583
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(12,009)	(143,817)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,809,244	1,660,143
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(476,099)	(398,532)
Debt Securities, Available-for-sale, Unrealized Loss Position	4,102,038	3,146,726
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(488,108)	(542,349)
U.S. Treasury and agencies
Investment Holdings [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	99,898	734,473
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,074)	(71,967)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	822,245	201,701
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(77,800)	(27,391)
Debt Securities, Available-for-sale, Unrealized Loss Position	922,143	936,174
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(78,874)	(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	103,256	160,078
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(580)	(10,037)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	169,231	60,381
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(21,030)	(18,004)
Debt Securities, Available-for-sale, Unrealized Loss Position	272,487	220,459
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(21,610)	(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	1,089,640	592,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(10,355)	(61,813)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,817,768	1,398,061
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(377,269)	(353,137)
Debt Securities, Available-for-sale, Unrealized Loss Position	2,907,408	1,990,093
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (387,624)	$ (414,950)