Investments (Gross Unrealized Losses And Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Less Than Twelve Months
Estimated Fair Value	$ 378,262	$ 766,882
Unrealized Loss	26,574	75,309
Estimated Fair Value	755,157	394,860
Twelve Months or Greater
Unrealized Loss	122,906	93,680
Estimated Fair Value	1,133,419	1,161,742
Unrealized Loss	149,480	168,989
Obligations of states and political subdivisions
Less Than Twelve Months
Estimated Fair Value	42,850	203,173
Unrealized Loss	1,084	21,929
Estimated Fair Value	155,074	13,359
Twelve Months or Greater
Unrealized Loss	18,118	2,395
Estimated Fair Value	197,924	216,532
Unrealized Loss	19,202	24,324
U.S. Government agencies
Less Than Twelve Months
Estimated Fair Value	318,110	533,611
Unrealized Loss	24,334	50,268
Estimated Fair Value	582,062	376,778
Twelve Months or Greater
Unrealized Loss	102,650	90,418
Estimated Fair Value	900,172	910,389
Unrealized Loss	126,984	140,686
Trust preferred securities
Less Than Twelve Months
Estimated Fair Value	0	0
Unrealized Loss	0	0
Estimated Fair Value	4,125	3,828
Twelve Months or Greater
Unrealized Loss	467	762
Estimated Fair Value	4,125	3,828
Unrealized Loss	467	762
Corporate securities
Less Than Twelve Months
Estimated Fair Value	10,251	22,972
Unrealized Loss	755	2,648
Estimated Fair Value	13,896	895
Twelve Months or Greater
Unrealized Loss	1,671	105
Estimated Fair Value	24,147	23,867
Unrealized Loss	2,426	2,753
Private label
Less Than Twelve Months
Estimated Fair Value	7,051	7,126
Unrealized Loss	401	464
Estimated Fair Value	0	0
Twelve Months or Greater
Unrealized Loss	0	0
Estimated Fair Value	7,051	7,126
Unrealized Loss	$ 401	$ 464