Investments - Available-For-Sale Securities in a Gross Unrealized Loss Position by Length of Time (Details) $ in Thousands	Mar. 31, 2026 USD ($) holding	Dec. 31, 2025 USD ($) holding
Investment grade
Fair value
Less than 12 months	$ 533,288	$ 144,472
12 months or longer	123,311	144,604
Total	656,599	289,076
Unrealized losses
Less than 12 months	4,779	433
12 months or longer	12,799	12,773
Total	$ 17,578	$ 13,206
No. of holdings | holding	642	371
Non-investment grade
Fair value
Less than 12 months	$ 112,650	$ 37,154
12 months or longer	16,026	15,975
Total	128,676	53,129
Unrealized losses
Less than 12 months	4,072	1,426
12 months or longer	2,054	1,193
Total	$ 6,126	$ 2,619
No. of holdings | holding	640	376
Corporate debt securities
Fair value
Less than 12 months	$ 404,232	$ 72,699
12 months or longer	37,403	41,040
Total	441,635	113,739
Unrealized losses
Less than 12 months	7,025	1,555
12 months or longer	2,566	1,630
Total	$ 9,591	$ 3,185
No. of holdings | holding	842	418
Collateralized debt obligations
Fair value
Less than 12 months	$ 89,699	$ 57,917
12 months or longer	3,395	3,909
Total	93,094	61,826
Unrealized losses
Less than 12 months	483	120
12 months or longer	52	44
Total	$ 535	$ 164
No. of holdings | holding	128	83
Commercial mortgage-backed securities
Fair value
Less than 12 months	$ 43,321	$ 16,103
12 months or longer	16,736	19,956
Total	60,057	36,059
Unrealized losses
Less than 12 months	275	59
12 months or longer	1,620	1,724
Total	$ 1,895	$ 1,783
No. of holdings | holding	94	70
Residential mortgage-backed securities
Fair value
Less than 12 months	$ 86,494	$ 17,675
12 months or longer	78,346	92,019
Total	164,840	109,694
Unrealized losses
Less than 12 months	848	27
12 months or longer	10,374	10,353
Total	$ 11,222	$ 10,380
No. of holdings | holding	176	146
Other debt securities
Fair value
Less than 12 months	$ 14,420	$ 3,936
12 months or longer	3,457	3,655
Total	17,877	7,591
Unrealized losses
Less than 12 months	118	39
12 months or longer	241	215
Total	$ 359	$ 254
No. of holdings | holding	40	27
U.S. Treasury
Fair value
Less than 12 months	$ 7,772	$ 13,296
12 months or longer	0	0
Total	7,772	13,296
Unrealized losses
Less than 12 months	102	59
12 months or longer	0	0
Total	$ 102	$ 59
No. of holdings | holding	2	3
Available-for-sale securities
Fair value
Less than 12 months	$ 645,938	$ 181,626
12 months or longer	139,337	160,579
Total	785,275	342,205
Unrealized losses
Less than 12 months	8,851	1,859
12 months or longer	14,853	13,966
Total	$ 23,704	$ 15,825
No. of holdings | holding	1,282	747