Summary of Investments (Net Realized Investment Gains and Losses and Proceeds) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net realized investment gains (losses):
Available-for-sale	$ 30	$ (8)	$ 0	$ 142
Allowance for credit losses	49	0	(10)	0
Trading securities
Change in fair value	1,601	501	(1,008)	2,247
Sales	(305)	92	(154)	92
Equity securities
Change in fair value	29,809	12,499	(60,838)	37,133
Sales	(15,406)	507	(15,586)	705
Mortgage loans allowance for credit losses	1	0	(4)	(15)
Real estate	0	0	(28)	0
Total net realized investment gains (losses)	15,779	13,591	(77,628)	40,304
Proceeds from sales	4,996	0	16,907	36,490
Gross realized gains	26	0	198	30
Gross realized losses	$ 113	$ 0	$ 495	$ 13