Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands	Sep. 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	$ 5,772,448	$ 1,486,583
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	245,427	143,817
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,704,482	1,660,143
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	631,090	398,532
Debt Securities, Available-for-sale, Unrealized Loss Position	8,476,930	3,146,726
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	876,517	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	643,453	734,473
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	11,464	71,967
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	792,079	201,701
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	109,074	27,391
Debt Securities, Available-for-sale, Unrealized Loss Position	1,435,532	936,174
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	120,538	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	819,008	160,078
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	43,750	10,037
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	157,996	60,381
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	32,430	18,004
Debt Securities, Available-for-sale, Unrealized Loss Position	977,004	220,459
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	76,180	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	4,309,987	592,032
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	190,213	61,813
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,754,407	1,398,061
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	489,586	353,137
Debt Securities, Available-for-sale, Unrealized Loss Position	6,064,394	1,990,093
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 679,799	$ 414,950