Investments - Net Realized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total other-than-temporary impairment losses:
OTTI losses	$ (978)	$ (490)	$ (13,200)
Portion of OTTI losses recognized in other comprehensive income before taxes	227	0	248
Net impairment losses recognized in earnings	(751)	(490)	(12,952)
Gross realized gains, available-for-sale fixed maturities	3,786	5,942	6,653
Gross realized (losses), available-for-sale fixed maturities	(538)	(5,799)	(3,123)
Net realized gains (losses), short-term investments	3	(1)	(2)
Net realized gains (losses), trading fixed maturities	74	(100)	0
Net realized gains (losses), equity investments	20,577	12,230	10,724
Net realized gains (losses), other investments	1,626	1,340	2,963
Change in unrealized holding gains (losses), trading fixed maturities	705	(317)	0
Change in unrealized holding gains (losses), equity investments	30,674	(52,707)	11,243
Change in unrealized holding gains (losses), convertible securities, carried at fair value	3,653	(3,849)	896
Other	65	263	7
Total net realized investment gains (losses)	59,874	(43,488)	16,409
State and municipal bonds
Total other-than-temporary impairment losses:
OTTI losses	0	0	(850)
Corporate debt
Total other-than-temporary impairment losses:
OTTI losses	(978)	(490)	(419)
Portion of OTTI losses recognized in other comprehensive income before taxes	227		248
Net impairment losses recognized in earnings	(800)	(500)	(200)
Investment in unconsolidated subsidiaries
Total other-than-temporary impairment losses:
OTTI losses	$ 0	$ 0	$ (11,931)