Investments - Schedule of Net Realized Investment Gains and Losses Recognized in Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Realized Investment Gains Losses [Abstract]
Gross gains from sales of available-for-sale securities	$ 632	$ 523	$ 1,816	$ 994
Gross losses from sales of available-for-sale securities	(559)	(1)	(675)	(286)
Credit losses on available-for-sale securities	(23)	(1,064)	(4,269)	(1,225)
Net gains (losses) recognized in net income during the period on equity securities	573	813	(4,552)	4,692
Gains (losses) from bifurcated options	26	14	42	14
Gains (losses) on trading securities	(7)		(7)	11
Net realized investment gains (losses)	$ 642	$ 285	$ (7,645)	$ 4,200