VARIABLE INTEREST ENTITIES (Details)		1 Months Ended	3 Months Ended			9 Months Ended
	Jan. 10, 2023 USD ($) note	Jul. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) account	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) account	Sep. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Variable Interest Entity [Line Items]
Number of segregated accounts | account			3			3
Assets			$ 40,843,076,000			$ 40,843,076,000			$ 36,552,878,000
Liabilities			27,592,225,000			27,592,225,000			26,692,215,000
Investments in other ventures, under equity method			101,103,000			101,103,000			79,750,000
Redeemable noncontrolling interests			5,662,234,000			5,662,234,000			4,535,389,000
Ceded premiums written			197,183,000		$ 398,950,000	1,179,559,000	$ 1,777,720,000
Ceded premiums earned			355,443,000		519,964,000	1,172,055,000	1,399,008,000
Vermeer
Variable Interest Entity [Line Items]
Redeemable noncontrolling interests			1,467,367,000		1,330,253,000	1,467,367,000	1,330,253,000	$ 1,590,408,000	1,490,840,000	$ 1,269,417,000	$ 1,197,782,000
Fontana
Variable Interest Entity [Line Items]
Redeemable noncontrolling interests			271,719,000		$ 261,530,000	271,719,000	261,530,000	$ 277,886,000	268,031,000	$ 268,143,000	$ 0
Variable Interest Entity, Primary Beneficiary | Upsilon Diversified
Variable Interest Entity [Line Items]
Investments in other ventures, under equity method			1,200,000			1,200,000			1,900,000
Variable Interest Entity, Primary Beneficiary | NOC1
Variable Interest Entity [Line Items]
Investments in other ventures, under equity method			1,600,000			1,600,000
Variable Interest Entity, Primary Beneficiary | Upsilon RFO Re Ltd.
Variable Interest Entity [Line Items]
Assets			2,700,000,000			2,700,000,000			3,700,000,000
Liabilities			2,700,000,000			2,700,000,000			3,700,000,000
Net assets			120,700,000			120,700,000			165,300,000
Variable Interest Entity, Primary Beneficiary | Upsilon Diversified
Variable Interest Entity [Line Items]
Assets			833,200,000			833,200,000			1,200,000,000
Liabilities			41,700,000			41,700,000			32,100,000
Variable Interest Entity, Primary Beneficiary | Upsilon Diversified | Upsilon RFO Re Ltd.
Variable Interest Entity [Line Items]
Investment owned, fair value			805,800,000			805,800,000			1,200,000,000
Variable Interest Entity, Primary Beneficiary | NOC1
Variable Interest Entity [Line Items]
Assets			159,600,000			159,600,000
Liabilities			600,000			600,000
Variable Interest Entity, Primary Beneficiary | Vermeer
Variable Interest Entity [Line Items]
Assets			1,600,000,000			1,600,000,000			1,600,000,000
Liabilities			172,900,000			172,900,000			144,900,000
Redeemable noncontrolling interests			1,500,000,000			1,500,000,000			1,500,000,000
Variable Interest Entity, Primary Beneficiary | Fontana
Variable Interest Entity [Line Items]
Assets			1,200,000,000			1,200,000,000			711,000,000
Liabilities			800,000,000			800,000,000			319,200,000
Redeemable noncontrolling interests			271,700,000			271,700,000			268,000,000
Variable Interest Entity, Primary Beneficiary | Third Party Investor | Upsilon RFO Re Ltd.
Variable Interest Entity [Line Items]
Payments of capital distribution						630,800,000	254,100,000
Net assets			800,000,000			800,000,000			1,200,000,000
Variable Interest Entity, Primary Beneficiary | Third Party Investor | Upsilon RFO Re Ltd. | Preference shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries						39,800,000	89,000,000.0
Variable Interest Entity, Primary Beneficiary | Third Party Investor | Upsilon Diversified
Variable Interest Entity [Line Items]
Payments of capital distribution						543,300,000	143,500,000
Variable Interest Entity, Primary Beneficiary | Third Party Investor | Upsilon Diversified | Preference shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries						30,000,000.0	82,500,000
Variable Interest Entity, Primary Beneficiary | Third Party Investor | NOC1 | Preference shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries						151,500,000
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | Upsilon RFO Re Ltd.
Variable Interest Entity [Line Items]
Payments of capital distribution						$ 79,500,000	$ 52,800,000
Variable interest entity, ownership percentage						13.50%	12.50%
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | Upsilon RFO Re Ltd. | Preference shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries						$ 10,200,000	$ 10,000,000.0
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | Upsilon Diversified
Variable Interest Entity [Line Items]
Payments of capital distribution						1,000,000.0	0
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | Upsilon Diversified | Preference shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries						100,000	0
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | NOC1 | Preference shares
Variable Interest Entity [Line Items]
Contributions to subsidiaries						1,500,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re
Variable Interest Entity [Line Items]
Assets			447,500,000			447,500,000			654,800,000
Liabilities			447,500,000			447,500,000			654,800,000
Number of notes issued | note	2
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re | Term loans
Variable Interest Entity [Line Items]
Investment in participating notes			3,400,000			3,400,000			5,700,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re | Eighty Five Million Principal At Risk Variable Rate Note
Variable Interest Entity [Line Items]
Face amount	$ 85,000,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re | One Hundred Million Principal At Risk Variable Rate Note
Variable Interest Entity [Line Items]
Face amount	$ 100,000,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re | Four Hundred Million Principal At Risk Variable Rate Note
Variable Interest Entity [Line Items]
Face amount			400,000,000			400,000,000
Variable Interest Entity, Not Primary Beneficiary | Langhorne Partners
Variable Interest Entity [Line Items]
Investments in other ventures, under equity method			$ 100,000			100,000			$ 100,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Holdings Ltd. | Langhorne Holdings LLC
Variable Interest Entity [Line Items]
Payments of capital distribution		$ 800,000		$ 1,500,000
Variable Interest Entity, Not Primary Beneficiary | Renaissance Reinsurance Ltd. | Mona Lisa Re
Variable Interest Entity [Line Items]
Ceded premiums written						32,800,000	39,600,000
Ceded premiums earned						24,400,000	29,400,000
Variable Interest Entity, Not Primary Beneficiary | DaVinci Reinsurance Ltd. | Mona Lisa Re
Variable Interest Entity [Line Items]
Ceded premiums written						8,200,000	9,900,000
Ceded premiums earned						6,100,000	$ 7,300,000
Variable Interest Entity, Not Primary Beneficiary | Medici | Mona Lisa Re
Variable Interest Entity [Line Items]
Payments of capital distribution						$ 16,500,000