Investments (Gross Unrealized Losses And Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Less Than Twelve Months
Estimated Fair Value	$ 72,624	$ 766,882
Unrealized Loss	17,075	75,309
Estimated Fair Value	1,002,434	394,860
Twelve Months or Greater
Unrealized Loss	197,408	93,680
Estimated Fair Value	1,075,058	1,161,742
Unrealized Loss	214,483	168,989
Obligations of states and political subdivisions
Less Than Twelve Months
Estimated Fair Value	25,076	203,173
Unrealized Loss	1,132	21,929
Estimated Fair Value	171,897	13,359
Twelve Months or Greater
Unrealized Loss	28,693	2,395
Estimated Fair Value	196,973	216,532
Unrealized Loss	29,825	24,324
U.S. Government agencies
Less Than Twelve Months
Estimated Fair Value	46,028	533,611
Unrealized Loss	15,895	50,268
Estimated Fair Value	795,988	376,778
Twelve Months or Greater
Unrealized Loss	165,252	90,418
Estimated Fair Value	842,016	910,389
Unrealized Loss	181,147	140,686
Private label
Less Than Twelve Months
Estimated Fair Value	0	7,126
Unrealized Loss	0	464
Estimated Fair Value	6,446	0
Twelve Months or Greater
Unrealized Loss	490	0
Estimated Fair Value	6,446	7,126
Unrealized Loss	490	464
Trust preferred securities
Less Than Twelve Months
Estimated Fair Value	0	0
Unrealized Loss	0	0
Estimated Fair Value	4,307	3,828
Twelve Months or Greater
Unrealized Loss	290	762
Estimated Fair Value	4,307	3,828
Unrealized Loss	290	762
Corporate securities
Less Than Twelve Months
Estimated Fair Value	1,520	22,972
Unrealized Loss	48	2,648
Estimated Fair Value	23,796	895
Twelve Months or Greater
Unrealized Loss	2,683	105
Estimated Fair Value	25,316	23,867
Unrealized Loss	$ 2,731	$ 2,753