Investments (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) item security	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) item security	Sep. 30, 2022 USD ($)	Dec. 31, 2022 security
Schedule of Available-for-sale Securities [Line Items]
Number of investment in unaffiliated issuers | item	320		320
Investment in debt securities (as percentage)	93.00%		93.00%
Gross gains on investments	$ 250	$ 500	$ 1,800	$ 1,700
Gross losses on investments	240	5	2,500	26
Proceeds from sale of investment securities	3,100	$ 200	61,600	$ 4,700
Debt securities, available-for-sale, allowance for expected credit losses	$ 0		$ 0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of investment in unaffiliated issuers | item	297		297
Investment grade securities (as percentage)	82.00%		82.00%
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Number of debt securities with unrealized loss | security	197		197		228
Number of debt securities with unrealized loss, less than 12 months | security	76		76		181
Number of debt securities with unrealized loss, greater than 12 months | security	121		121		47