Investments (Narrative) (Details) $ in Thousands	6 Months Ended
Jun. 30, 2022 USD ($) item security	Dec. 31, 2021 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 509,787	$ 529,811
Number of investments in a single issuer exceeds 10% of shareholders' equity \| item	0
Percent of shareholders equity benchmark for investments in a single issuer	10.00%
Number of debt securities \| security	553	227
Fair value of temporarily impaired securities	$ 479,463	$ 271,525
Unrealized Losses	44,808	4,666
Total unrealized loss position increased over prior year	$ 40,100
Number Of Bond Issuers \| item	203
Number Of Bonds Below Investment Grade \| item	0
General Obligation Bonds	63.00%
Equity securities	$ 495	481
Texas [Member]
Schedule of Available-for-sale Securities [Line Items]
Percent of Investment Portfolio	14.00%
Pennsylvania [Member]
Schedule of Available-for-sale Securities [Line Items]
Percent of Investment Portfolio	11.00%
CALIFORNIA
Schedule of Available-for-sale Securities [Line Items]
Percent of Investment Portfolio	11.00%
MICHIGAN
Schedule of Available-for-sale Securities [Line Items]
Percent of Investment Portfolio	10.00%
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 24,829	$ 24,939
Number of debt securities \| security	42	20
Fair value of temporarily impaired securities	$ 21,524	$ 10,648
Unrealized Losses	982	188
Public Funds And Trust Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 196,100	$ 160,300
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of equity investments \| item	1

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