Investments - Schedule of Realized Gain (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt and Equity Securities, Gain (Loss)
Gross realized gains	$ 27,432	$ 69	$ 28,975	$ 691
Gross realized losses	(2,464)	(51)	(4,016)	(505)
Net realized gains (losses)	24,968	18	24,959	186
Fair Value at Sale
Fair value at sale	146,153	37,065	242,651	133,749
Fair value at sale	10,712	2,057	20,949	38,859
Net fair value at sale	156,865	39,122	263,600	172,608
Fixed Maturities
Debt and Equity Securities, Gain (Loss)
Gross realized gains	708	66	1,425	597
Gross realized losses	(45)	(48)	(439)	(287)
Fair Value at Sale
Fair value at sale	47,153	34,282	139,609	129,364
Fair value at sale	1,203	2,033	7,942	36,661
Equity Securities
Debt and Equity Securities, Gain (Loss)
Gross realized gains	26,724	3	27,550	94
Gross realized losses	(2,419)	(3)	(3,577)	(217)
Fair Value at Sale
Fair value at sale	97,725	272	101,696	814
Fair value at sale	9,509	14	12,879	1,163
Short-term Investments
Debt and Equity Securities, Gain (Loss)
Gross realized gains	0	0	0	0
Gross realized losses	0	0	0	(1)
Fair Value at Sale
Fair value at sale	1,275	2,511	1,346	3,571
Fair value at sale	$ 0	$ 10	$ 128	$ 1,035