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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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Investments - Schedule of Private Debt and Equity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2026 USD ($) note	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)	Apr. 11, 2025 note
Net Investment Income [Line Items]
Carrying Value	$ 67,413		$ 64,152
Investment Income	1,815	$ 200
Renewable energy LLCs
Net Investment Income [Line Items]
Carrying Value	7,193		7,274
Investment Income	(30)	0
Limited partnerships
Net Investment Income [Line Items]
Carrying Value	15,027		13,477
Investment Income	1,174	9
Private debt
Net Investment Income [Line Items]
Carrying Value	45,193		43,401
Investment Income	671	191
Excess & Surplus Lines
Net Investment Income [Line Items]
Carrying Value	67,044		63,783
Investment Income	$ 1,815	200
Excess & Surplus Lines \| TPG Angelo Gordon
Net Investment Income [Line Items]
Number of notes maturing in 2031 \| note	2
Number of notes maturing in 2035 \| note	2
Excess & Surplus Lines \| Sixth Street
Net Investment Income [Line Items]
Number of notes maturing in 2035 \| note				3
Number of notes maturing in 2064 \| note				3
Excess & Surplus Lines \| Notes receivable one \| Sixth Street
Net Investment Income [Line Items]
Rate of interest				6.79%
Excess & Surplus Lines \| Notes receivable two \| Sixth Street
Net Investment Income [Line Items]
Rate of interest				8.04%
Excess & Surplus Lines \| Notes receivable three \| Sixth Street
Net Investment Income [Line Items]
Rate of interest				9.04%
Excess & Surplus Lines \| Renewable energy LLCs
Net Investment Income [Line Items]
Carrying Value	$ 7,193		7,274
Investment Income	(30)	0
Excess & Surplus Lines \| Renewable energy LLCs \| Investment in LLC
Net Investment Income [Line Items]
Cash distributions from LLCs	$ 50	48
Excess & Surplus Lines \| Renewable energy LLCs \| Minimum \| Investment in LLC \| Various LLCs
Net Investment Income [Line Items]
Ownership percentage	3.60%
Excess & Surplus Lines \| Renewable energy LLCs \| Maximum \| Investment in LLC \| Various LLCs
Net Investment Income [Line Items]
Ownership percentage	5.10%
Excess & Surplus Lines \| Limited partnerships
Net Investment Income [Line Items]
Carrying Value	$ 14,658		13,108
Investment Income	1,174	9
Outstanding commitments to invest	11,100
Excess & Surplus Lines \| Private debt
Net Investment Income [Line Items]
Carrying Value	45,193		43,401
Investment Income	$ 671	191
Excess & Surplus Lines \| Private speciality credit
Net Investment Income [Line Items]
Number of notes issued \| note	10
Excess & Surplus Lines \| Private speciality credit \| Notes receivable one
Net Investment Income [Line Items]
Rate of interest	4.25%
Excess & Surplus Lines \| Private speciality credit \| Notes receivable two
Net Investment Income [Line Items]
Rate of interest	5.25%
Excess & Surplus Lines \| Private speciality credit \| Notes receivable three
Net Investment Income [Line Items]
Rate of interest	6.50%
Excess & Surplus Lines \| Private speciality credit \| Notes receivable four
Net Investment Income [Line Items]
Rate of interest	8.00%
Excess & Surplus Lines \| Private speciality credit \| Notes Receivable Five
Net Investment Income [Line Items]
Rate of interest	6.00%
Excess & Surplus Lines \| Private speciality credit \| Notes Receivable Six
Net Investment Income [Line Items]
Rate of interest	7.00%
Excess & Surplus Lines \| Private speciality credit \| Notes Receivable Seven
Net Investment Income [Line Items]
Rate of interest	8.00%
Excess & Surplus Lines \| Private Specialty Credit
Net Investment Income [Line Items]
Commitment to invest in notes receivable	$ 78,300
Corporate & Other
Net Investment Income [Line Items]
Carrying Value	369		369
Investment Income	0	0
Corporate & Other \| Renewable energy LLCs
Net Investment Income [Line Items]
Carrying Value	0		0
Investment Income	0	0
Corporate & Other \| Limited partnerships
Net Investment Income [Line Items]
Carrying Value	369		369
Investment Income	0	0
Corporate & Other \| Private debt
Net Investment Income [Line Items]
Carrying Value	0		$ 0
Investment Income	$ 0	$ 0