Investments - Available-For-Sale Securities in a Gross Unrealized Loss Position by Length of Time (Details) $ in Thousands	Mar. 31, 2025 USD ($) holding	Dec. 31, 2024 USD ($) holding
Investment grade
Fair value
Less than 12 months	$ 221,033	$ 280,332
12 months or longer	243,010	260,480
Total	464,043	540,812
Unrealized losses
Less than 12 months	1,898	3,701
12 months or longer	18,704	22,664
Total	$ 20,602	$ 26,365
No. of holdings | holding	555	616
Non-investment grade
Fair value
Less than 12 months	$ 69,127	$ 28,972
12 months or longer	26,899	27,561
Total	96,026	56,533
Unrealized losses
Less than 12 months	1,604	702
12 months or longer	1,892	2,080
Total	$ 3,496	$ 2,782
No. of holdings | holding	599	370
Corporate debt securities
Fair value
Less than 12 months	$ 170,976	$ 197,619
12 months or longer	144,217	156,059
Total	315,193	353,678
Unrealized losses
Less than 12 months	2,383	2,486
12 months or longer	4,915	6,199
Total	$ 7,298	$ 8,685
No. of holdings | holding	754	567
Collateralized debt obligations
Fair value
Less than 12 months	$ 64,839	$ 33,686
12 months or longer	8,766	11,762
Total	73,605	45,448
Unrealized losses
Less than 12 months	179	71
12 months or longer	214	316
Total	$ 393	$ 387
No. of holdings | holding	112	77
Commercial mortgage-backed securities
Fair value
Less than 12 months	$ 15,244	$ 28,333
12 months or longer	22,838	24,966
Total	38,082	53,299
Unrealized losses
Less than 12 months	149	407
12 months or longer	2,097	2,578
Total	$ 2,246	$ 2,985
No. of holdings | holding	92	131
Residential mortgage-backed securities
Fair value
Less than 12 months	$ 31,709	$ 38,003
12 months or longer	89,244	90,209
Total	120,953	128,212
Unrealized losses
Less than 12 months	752	1,289
12 months or longer	12,951	15,173
Total	$ 13,703	$ 16,462
No. of holdings | holding	162	169
Other debt securities
Fair value
Less than 12 months	$ 7,392	$ 11,663
12 months or longer	4,844	5,045
Total	12,236	16,708
Unrealized losses
Less than 12 months	39	150
12 months or longer	419	478
Total	$ 458	$ 628
No. of holdings | holding	34	42
Available-for-sale securities
Fair value
Less than 12 months	$ 290,160	$ 309,304
12 months or longer	269,909	288,041
Total	560,069	597,345
Unrealized losses
Less than 12 months	3,502	4,403
12 months or longer	20,596	24,744
Total	$ 24,098	$ 29,147
No. of holdings | holding	1,154	986