Investments - Net Realized and Unrealized Gains (Losses) on Investment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Gain (Loss) on Securities [Line Items]
Other investments, gross gains		$ 0
Other investments, gross losses		(145)
Other investments, net		(145)
Net realized gains (losses) on investment, gross gains	$ 11,039	2,424
Net realized gains (losses) on investment, gross losses	(1)	(13,525)
Net realized gains (losses) on investment, net	11,038	(11,101)
Proceeds from sales of fixed maturities classified as available-for-sale	224,471	84,361
Deferred income tax	19		$ (96)
Net unrealized gains (losses), net of deferred income tax	(22,125)		21,996
Change, net of deferred income tax	(44,121)	81,758
Fixed maturities
Gain (Loss) on Securities [Line Items]
AFS fixed maturities, gross gains	10,932	2,424
AFS fixed maturities, gross losses	(1)	(13,380)
AFS fixed maturities, net	10,931	$ (10,956)
Other Debt Obligations
Gain (Loss) on Securities [Line Items]
Other investments, gross gains	107
Other investments, gross losses	0
Other investments, net	107
Available-for-sale securities | Fixed maturities
Gain (Loss) on Securities [Line Items]
Fixed maturities	$ (22,144)		$ 22,092