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INVESTMENTS - Equity Method Investments (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended				18 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2016	Jun. 30, 2026
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	$ 10,459	$ 7,340
Advances to affiliate during the period	143,209	$ 94,161
Loan advances made	316,342		$ 231,542				$ 316,342
Monarch Point Re \| Loan With Monarch Point Re \| Related Party
Schedule of Equity Method Investments [Line Items]
Advances to affiliate during the period	183,000		227,000
Loan advances made	313,000		228,000				313,000
Other liabilities	$ 8,000		$ 5,000				$ 8,000
Monarch Point Re \| Loan With Monarch Point Re \| Related Party \| Minimum
Schedule of Equity Method Investments [Line Items]
Stated interest rate (as a percent)	4.20%		4.30%
Monarch Point Re \| Loan With Monarch Point Re \| Related Party \| Maximum
Schedule of Equity Method Investments [Line Items]
Stated interest rate (as a percent)	4.40%		4.80%
Harrington Re
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments						$ 108,000
Equity method investment, ownership percentage (as a percent)	18.00%		23.00%	22.00%		19.00%	18.00%
Monarch Point Re (ISAC) Ltd and Monarch Point Re (ISA 2023) Ltd
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments					$ 22,000
Equity method investment, ownership percentage (as a percent)					18.00%
Monarch Point Re (ISA 2024) Ltd
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments				$ 14,000
Equity method investment, ownership percentage (as a percent)				18.00%
Monarch Point Re (ISA 2025) Ltd
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments							$ 13,000
Equity method investment, ownership percentage (as a percent)	18.00%						18.00%
Monarch Point Re (ISA 2026) Ltd
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	$ 8,000
Equity method investment, ownership percentage (as a percent)	18.00%						18.00%