Investments (Aggregate Carrying And Approximate Market Values Of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Total	$ 1,503,572	$ 1,479,545
Gross Unrealized Gains	1,585	2,870
Gross Unrealized Losses	157,500	144,278
Estimated Fair Value	1,347,657	1,338,137
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Total	227,434	228,456
Gross Unrealized Gains	217	371
Gross Unrealized Losses	17,127	16,089
Estimated Fair Value	210,524	212,738
U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Total	1,236,587	1,211,484
Gross Unrealized Gains	1,316	2,362
Gross Unrealized Losses	138,106	125,753
Estimated Fair Value	1,099,797	1,088,093
Private label
Debt Securities, Available-for-sale [Line Items]
Total	6,981	6,997
Gross Unrealized Gains	0	0
Gross Unrealized Losses	284	293
Estimated Fair Value	6,697	6,704
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Total	4,600	4,599
Gross Unrealized Gains	0	0
Gross Unrealized Losses	151	321
Estimated Fair Value	4,449	4,278
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Total	27,970	28,009
Gross Unrealized Gains	52	137
Gross Unrealized Losses	1,832	1,822
Estimated Fair Value	$ 26,190	$ 26,324