Investments (Aggregate Carrying And Approximate Market Values Of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Total	$ 1,586,870	$ 1,673,864
Gross Unrealized Gains	374	645
Gross Unrealized Losses	167,311	168,989
Estimated Fair Value	1,419,933	1,505,520
Certificates of deposit, at carrying value	200	700
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Total	245,922	292,293
Gross Unrealized Gains	160	346
Gross Unrealized Losses	20,481	24,324
Estimated Fair Value	225,601	268,315
U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Total	1,300,980	1,342,666
Gross Unrealized Gains	214	299
Gross Unrealized Losses	142,736	140,686
Estimated Fair Value	1,158,458	1,202,279
Private label
Debt Securities, Available-for-sale [Line Items]
Total	7,288	7,695
Gross Unrealized Gains	0	0
Gross Unrealized Losses	498	464
Estimated Fair Value	6,790	7,231
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Total	4,595	4,590
Gross Unrealized Gains	0	0
Gross Unrealized Losses	403	762
Estimated Fair Value	4,192	3,828
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Total	28,085	26,620
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,193	2,753
Estimated Fair Value	$ 24,892	$ 23,867