Investments (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) security	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) item security	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 439,471		$ 439,471		$ 486,836
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	570		570		591
Fair value of temporarily impaired securities	$ 434,016		$ 434,016		$ 474,847
Unrealized Losses	57,329		57,329		61,531
Decrease in unrealized loss position			4,200
Equity securities	380		380		411
Debt Securities, Available-for-sale, Realized Gain (Loss)	(517)	$ (19)	(1,119)	$ (19)
Proceeds from Sale of Debt Securities, Available-for-sale	7,262	$ 82	40,117	$ 82
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 22,830		$ 22,830		$ 24,239
Number of debt securities | security	51		51		46
Fair value of temporarily impaired securities	$ 22,830		$ 22,830		$ 22,589
Unrealized Losses	3,496		3,496		2,077
Public Funds And Trust Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 151,700		$ 151,700		$ 208,900
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of equity investments | item			1