Investments - Cost and Fair Value, Net of Credit Loss Allowance, of Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Available-for-sale securities:
Amortized cost	$ 1,065,956
Total available-for-sale securities	1,043,615
Held-to-maturity securities:
Total fixed maturity securities, net	1,070,789
Gross unrealized gains	6,907
Gross unrealized losses	29,147
Estimated fair value	1,048,549
Fair value of loaned securities	7,285	$ 0
Corporate debt securities
Available-for-sale securities:
Amortized cost	647,861	600,639
Gross unrealized gains	4,767	4,594
Gross unrealized losses	8,685	16,545
Total available-for-sale securities	643,943	588,688
Collateralized debt obligations
Available-for-sale securities:
Amortized cost	114,142	114,400
Gross unrealized gains	372	156
Gross unrealized losses	387	2,088
Total available-for-sale securities	114,127	112,468
Commercial mortgage-backed securities
Available-for-sale securities:
Amortized cost	126,509	106,019
Gross unrealized gains	1,458	1,410
Gross unrealized losses	2,985	4,709
Total available-for-sale securities	124,982	102,720
Residential mortgage-backed securities
Available-for-sale securities:
Amortized cost	150,212	153,633
Gross unrealized gains	62	69
Gross unrealized losses	16,462	13,647
Total available-for-sale securities	133,812	140,055
Other debt securities
Available-for-sale securities:
Amortized cost	27,232	17,862
Gross unrealized gains	147	136
Gross unrealized losses	628	688
Total available-for-sale securities	26,751	17,310
Debt securities
Available-for-sale securities:
Amortized cost	1,065,956	992,553
Gross unrealized gains	6,806	6,365
Gross unrealized losses	29,147	37,677
Total available-for-sale securities	1,043,615	$ 961,241
Held-to-maturity securities
Held-to-maturity securities:
Amortized cost	4,833
Gross unrealized gains	101
Gross unrealized losses	0
Fair Value	$ 4,934