Investments - Other Than Temporarily Impaired and Credit Ratings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($) security	Dec. 31, 2020 USD ($)
Schedule of Fixed Maturities Table [Line Items]
Other-than-temporary impairment losses	$ 0	$ 0	$ 0	$ 1,506
Number of securities with other-than-temporary impairment losses \| security				2
Amortized cost	911,547		911,547		$ 1,163,923
Fair value	$ 938,685		$ 938,685		$ 1,213,411
% of Total fair value	100.00%		100.00%		100.00%
AAA
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 124,254		$ 124,254		$ 96,453
Fair value	$ 124,569		$ 124,569		$ 97,515
% of Total fair value	13.30%		13.30%		8.00%
AA+, AA, AA-
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 72,130		$ 72,130		$ 114,751
Fair value	$ 73,304		$ 73,304		$ 118,534
% of Total fair value	7.80%		7.80%		9.80%
A+, A, A-
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 220,396		$ 220,396		$ 265,725
Fair value	$ 227,914		$ 227,914		$ 281,364
% of Total fair value	24.30%		24.30%		23.20%
BBB+, BBB, BBB-
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 225,475		$ 225,475		$ 274,406
Fair value	$ 236,805		$ 236,805		$ 292,493
% of Total fair value	25.20%		25.20%		24.10%
BB+ or lower
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 42,291		$ 42,291		$ 45,996
Fair value	$ 44,186		$ 44,186		$ 47,566
% of Total fair value	4.70%		4.70%		3.90%
U.S. treasury bonds
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 78,481		$ 78,481		$ 94,468
Fair value	$ 78,454		$ 78,454		$ 94,502
% of Total fair value	8.40%		8.40%		7.80%
U.S. agency bonds
Schedule of Fixed Maturities Table [Line Items]
Amortized cost	$ 148,520		$ 148,520		$ 272,124
Fair value	$ 153,453		$ 153,453		$ 281,437
% of Total fair value	16.30%		16.30%		23.20%