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FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	$ 25,185,430		$ 25,185,430		$ 24,884,323
Debt	2,330,907		2,330,907		2,329,201
Asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	1,688,500		1,688,500		1,606,790
Other Investments \| Income Statement Location [Axis]: us-gaap:NonoperatingGainsLosses
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized gains recognized in earnings	83,000	$ 68,700	900	$ 19,800
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	311,464		311,464		154,115
Debt	99,300		99,300		99,200
Long-term debt	98,300		98,300		100,200
Significant Unobservable Inputs (Level 3) \| Asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	91,767		91,767		39,859
Significant Unobservable Inputs (Level 3) \| Asset-backed \| Non-company unobservable input
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	50,200		50,200		0
Significant Unobservable Inputs (Level 3) \| Asset-backed \| Discounted cash flow
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	41,609		41,609		39,859
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	15,565,754		15,565,754		14,088,705
Debt	2,200,000		2,200,000		2,200,000
Long-term debt	2,300,000		2,300,000		2,300,000
Significant Other Observable Inputs (Level 2) \| Asset-backed
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity investments trading	$ 1,596,733		$ 1,596,733		$ 1,566,931