Summary of Investments (Net Realized Investment Gains and Losses and Proceeds) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net realized investment gains (losses):
Available-for-sale	$ 52	$ 129	$ 52	$ 271
Allowance for credit losses	2	0	(8)	0
Trading securities
Change in fair value	248	43	(760)	2,290
Sales	134	8	(20)	100
Equity securities
Change in fair value	21,962	9,692	(38,876)	46,825
Sales	(7,186)	(50)	(22,772)	655
Mortgage loans allowance for credit losses	0	0	(4)	(15)
Real estate	0	0	(28)	0
Total net realized investment gains (losses)	15,212	9,822	(62,416)	50,126
Proceeds from sales	0	0	16,907	36,490
Gross realized gains	0	0	198	30
Gross realized losses	$ 0	$ 0	$ 495	$ 13