Investments (Gross Unrealized Losses And Fair Value Of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Less Than Twelve Months
Estimated Fair Value	$ 575,961	$ 73,478
Unrealized Loss	5,799	245
Estimated Fair Value	30,155	4,135
Twelve Months or Greater
Unrealized Loss	199	457
Estimated Fair Value	606,116	77,613
Unrealized Loss	5,998	702
Obligations of states and political subdivisions
Less Than Twelve Months
Estimated Fair Value	58,991	10,578
Unrealized Loss	516	139
Estimated Fair Value	2,410	0
Twelve Months or Greater
Unrealized Loss	73	0
Estimated Fair Value	61,401	10,578
Unrealized Loss	589	139
U.S. Government agencies
Less Than Twelve Months
Estimated Fair Value	515,972	62,412
Unrealized Loss	5,281	105
Estimated Fair Value	23,296	35
Twelve Months or Greater
Unrealized Loss	8	0
Estimated Fair Value	539,268	62,447
Unrealized Loss	5,289	105
Trust preferred securities
Less Than Twelve Months
Estimated Fair Value	0	0
Unrealized Loss	0	0
Estimated Fair Value	4,449	4,100
Twelve Months or Greater
Unrealized Loss	118	457
Estimated Fair Value	4,449	4,100
Unrealized Loss	118	457
Corporate securities
Less Than Twelve Months
Estimated Fair Value	998	488
Unrealized Loss	2	1
Estimated Fair Value	0	0
Twelve Months or Greater
Unrealized Loss	0	0
Estimated Fair Value	998	488
Unrealized Loss	$ 2	$ 1