Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 4,495,441	$ 1,292,794
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(57,341)	(12,009)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,755,606	2,809,244
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(510,546)	(476,099)
Debt Securities, Available-for-sale, Unrealized Loss Position	7,251,047	4,102,038
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(567,887)	(488,108)
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	338,230	99,898
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,305)	(1,074)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	816,265	822,245
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(82,674)	(77,800)
Debt Securities, Available-for-sale, Unrealized Loss Position	1,154,495	922,143
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(85,979)	(78,874)
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	297,204	103,256
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,464)	(580)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	182,355	169,231
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(22,685)	(21,030)
Debt Securities, Available-for-sale, Unrealized Loss Position	479,559	272,487
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(25,149)	(21,610)
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	3,860,007	1,089,640
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(51,572)	(10,355)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,756,986	1,817,768
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(405,187)	(377,269)
Debt Securities, Available-for-sale, Unrealized Loss Position	5,616,993	2,907,408
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (456,759)	$ (387,624)