FAIR VALUE MEASUREMENTS - Quantitative Information Used as Level 3 Inputs (Details) $ in Thousands	Mar. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	$ 2,700,655	$ 2,494,954
Other liabilities	(3,157)	(5,331)
Fair Value, Measurements, Recurring
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	2,700,655	2,494,954
Total assets and (liabilities) measured at fair value on a recurring basis using Level 3 inputs	23,140,465	22,175,694
Fair Value, Measurements, Recurring | Assumed and ceded (re)insurance contracts
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other liabilities	(1,112)	(1,832)
Fair Value, Measurements, Recurring | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	167,532	166,780
Other liabilities	(1,112)	(1,832)
Total assets and (liabilities) measured at fair value on a recurring basis using Level 3 inputs	166,420	164,948
Fair Value, Measurements, Recurring | Internal valuation model | Fair Value (Level 3) | Assumed and ceded (re)insurance contracts, group two
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other liabilities	(1,112)	(1,832)
Fair Value, Measurements, Recurring | Direct private equity investments | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	67,532	66,780
Fair Value, Measurements, Recurring | Direct private equity investments | Internal valuation model | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	67,532	66,780
Fair Value, Measurements, Recurring | Term loans | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	100,000	100,000
Fair Value, Measurements, Recurring | Term loans | Internal valuation model | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	100,000	100,000
Fair Value, Measurements, Recurring | Term loans | Discounted cash flow | Fair Value (Level 3)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments	$ 100,000	$ 100,000
Discount rate | Fair Value, Measurements, Recurring | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual | Assumed and ceded (re)insurance contracts, group two
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share)	0.036	0.040
Discount rate | Fair Value, Measurements, Recurring | Direct private equity investments | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share) | $ / shares	0.090	0.075
Liquidity discount | Fair Value, Measurements, Recurring | Direct private equity investments | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share) | $ / shares	0.150	0.150
Credit spread adjustment | Fair Value, Measurements, Recurring | Term loans | Discounted cash flow | Fair Value (Level 3) | Weighted Average or Actual
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share) | $ / shares	0.002	0.002
Risk premium | Fair Value, Measurements, Recurring | Term loans | Discounted cash flow | Fair Value (Level 3) | Weighted Average or Actual
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share) | $ / shares	0.026	0.026
Net undiscounted cash flows | Fair Value, Measurements, Recurring | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual | Assumed and ceded (re)insurance contracts, group two
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share)	14,964,000	14,734,000
Expected loss ratio | Fair Value, Measurements, Recurring | Internal valuation model | Fair Value (Level 3) | Weighted Average or Actual | Assumed and ceded (re)insurance contracts, group two
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Significant observable and unobservable inputs (in dollars per share)	0.043	0.058