Investments - Schedule of Investments Reconciliation (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Original or amortized cost	$ 1,530,689	$ 1,813,426
Gross unrealized gains	30,619	39,731
Gross unrealized losses	(52,764)	(17,639)
Fixed maturities	1,508,544	1,835,518
U.S. treasury bonds
Schedule of Investments [Line Items]
Original or amortized cost	84,959	94,921
Gross unrealized gains	1,185	704
Gross unrealized losses	(1)	0
Fixed maturities	86,143	95,625
U.S. agency bonds – mortgage-backed
Schedule of Investments [Line Items]
Original or amortized cost	495,747	533,296
Gross unrealized gains	19,510	6,717
Gross unrealized losses	(132)	(1,291)
Fixed maturities	515,125	538,722
Non-U.S. government and supranational bonds
Schedule of Investments [Line Items]
Original or amortized cost	7,290	11,796
Gross unrealized gains	93	294
Gross unrealized losses	(200)	(91)
Fixed maturities	7,183	11,999
Asset-backed securities
Schedule of Investments [Line Items]
Original or amortized cost	187,255	187,881
Gross unrealized gains	495	821
Gross unrealized losses	(14,715)	(532)
Fixed maturities	173,035	188,170
Corporate bonds
Schedule of Investments [Line Items]
Original or amortized cost	755,438	981,441
Gross unrealized gains	9,336	31,140
Gross unrealized losses	(37,716)	(15,725)
Fixed maturities	$ 727,058	996,856
Municipal bonds
Schedule of Investments [Line Items]
Original or amortized cost		4,091
Gross unrealized gains		55
Gross unrealized losses		0
Fixed maturities		$ 4,146