Investments - Amortized Cost and Estimated Fair Value, Net of Credit Loss Allowance, of Fixed Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Available-for-sale securities, Amortized cost
Due in one year or less	$ 37,273
Due after one year through five years	552,240
Due after five years through ten years	249,274
Due after ten years	524,441
Amortized cost	1,363,228
Held-to-maturity securities, Amortized cost
Held-to-maturity securities - due after ten years	4,833
Available-for-sale securities, Estimated fair value
Due in one year or less	37,302
Due after one year through five years	558,399
Due after five years through ten years	251,231
Due after ten years	517,896
Estimated fair value	1,364,828
Held-to-maturity securities, Estimated fair value
Held-to-maturity securities - due after ten years	4,863
Amortized cost	1,368,061	$ 1,070,789
Estimated fair value	1,369,691	$ 1,048,549
Fair value of securities lent	$ 64,500