Investments, Net Realized and Unrealized Gains (Losses) on Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Components of net realized and unrealized gains (losses) on investments [Abstract]
Gross gains on available-for-sale fixed income securities during the period	$ 2,875	$ 2,407	$ 8,088	$ 9,710
Gross losses on available-for-sale fixed income securities sold during the period	(2,662)	(2,728)	(7,552)	(9,409)
Impairment losses on investments	(588)	(58)	(1,046)	(404)
Change in value of limited partnership investments	62	278	(1,201)	1,000
Gains on equity securities [Abstract]
Realized gains (losses) on equity securities sold during the period	(252)	1,520	(9,460)	1,571
Unrealized gains (losses) on equity securities held at the end of the period	709	(1,294)	(5,825)	6,573
Realized and unrealized gains (losses) on equity securities during the period	457	226	(15,285)	8,144
Net realized and unrealized gains (losses) on investments	144	$ 125	(16,996)	$ 9,041
Recorded write down to earnings	$ 588		1,046
Undistributed earnings, net of tax			$ 4,038