v3.26.1
VARIABLE INTEREST ENTITIES (Details)
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
USD ($)
account
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
account
Jun. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Variable Interest Entity [Line Items]          
Number of segregated accounts | account 4   4    
Assets $ 55,195,613,000   $ 55,195,613,000   $ 53,800,390,000
Liabilities 36,032,051,000   36,032,051,000   34,589,641,000
Investments 36,213,100,000   36,213,100,000   36,073,209,000
Other assets 422,106,000   422,106,000   328,087,000
Reserve for claims and claim expenses (Note 6) 22,269,134,000 $ 22,913,763,000 22,269,134,000 $ 22,913,763,000 22,302,345,000
Other liabilities 649,551,000   649,551,000   856,302,000
Investments in other ventures, under equity method 149,337,000   149,337,000   121,871,000
Ceded premiums written 717,464,000 650,910,000 1,518,041,000 1,362,884,000  
Ceded premiums earned 504,561,000 $ 449,130,000 944,077,000 835,570,000  
Variable Interest Entity, Primary Beneficiary | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Assets 578,600,000   578,600,000   653,000,000.0
Liabilities 577,700,000   577,700,000   652,100,000
Investments 496,200,000   496,200,000   526,800,000
Other assets 82,300,000   82,300,000   126,200,000
Reserve for claims and claim expenses (Note 6) 257,900,000   257,900,000   305,800,000
Other liabilities 319,800,000   319,800,000   346,300,000
Net assets 34,400,000   34,400,000   32,700,000
Variable Interest Entity, Primary Beneficiary | Investors of Upsilon RFO Diversified I, II and III | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Payments of capital distribution     18,500,000 191,700,000  
Net assets 286,100,000   286,100,000   $ 264,800,000
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Payments of capital distribution     $ 2,000,000.0 23,600,000  
Variable interest entity, ownership percentage     13.00%   12.70%
Variable Interest Entity, Primary Beneficiary | Investors of Upsilon RFO Diversified IV | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Payments of capital distribution     $ 19,100,000 21,900,000  
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Diversified Fund          
Variable Interest Entity [Line Items]          
Investments in other ventures, under equity method 400,000   400,000   $ 400,000
Variable Interest Entity, Not Primary Beneficiary | NOC1          
Variable Interest Entity [Line Items]          
Investments in other ventures, under equity method 0   0   1,900,000
Variable Interest Entity, Not Primary Beneficiary | AlphaCat Managers Ltd          
Variable Interest Entity [Line Items]          
Investments in other ventures, under equity method 2,200,000   2,200,000   2,200,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Diversified Fund          
Variable Interest Entity [Line Items]          
Assets 268,400,000   268,400,000   278,400,000
Liabilities 25,700,000   25,700,000   42,600,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Diversified Fund | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Investment owned, fair value 263,700,000   263,700,000   254,700,000
Variable Interest Entity, Not Primary Beneficiary | NOC1          
Variable Interest Entity [Line Items]          
Assets 0   0   192,700,000
Liabilities 0   0   500,000
Variable Interest Entity, Not Primary Beneficiary | Stratos          
Variable Interest Entity [Line Items]          
Assets 272,500,000   272,500,000   261,900,000
Liabilities 1,400,000   1,400,000   200,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re          
Variable Interest Entity [Line Items]          
Assets 941,800,000   941,800,000   1,100,000,000
Liabilities 941,800,000   941,800,000   1,100,000,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re | Balance Sheet Location [Axis]: us-gaap:OtherLongTermInvestments          
Variable Interest Entity [Line Items]          
Investment in participating notes 4,500,000   4,500,000   3,400,000
Variable Interest Entity, Not Primary Beneficiary | AlphaCat Managers Ltd          
Variable Interest Entity [Line Items]          
Assets 429,300,000   429,300,000   1,100,000,000
Liabilities 196,600,000   196,600,000   496,100,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Holdings Ltd. | RenaissanceRe Upsilon Diversified Fund          
Variable Interest Entity [Line Items]          
Payments of capital distribution       200,000  
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Holdings Ltd. | NOC1          
Variable Interest Entity [Line Items]          
Payments of capital distribution 2,000,000.0        
Variable Interest Entity, Not Primary Beneficiary | Investors of Upsilon RFO Diversified IV | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Net assets 100,800,000   100,800,000   $ 101,800,000
Variable Interest Entity, Not Primary Beneficiary | Third Party Investor | RenaissanceRe Upsilon Diversified Fund          
Variable Interest Entity [Line Items]          
Payments of capital distribution     14,500,000 177,400,000  
Variable Interest Entity, Not Primary Beneficiary | Third Party Investor | RenaissanceRe Upsilon Diversified Fund | Preference shares          
Variable Interest Entity [Line Items]          
Payments to acquire Interest in subsidiaries and affiliates       17,500,000  
Variable Interest Entity, Not Primary Beneficiary | Third Party Investor | NOC1          
Variable Interest Entity [Line Items]          
Payments of capital distribution $ 196,600,000        
Variable Interest Entity, Not Primary Beneficiary | Renaissance Reinsurance Ltd. | Mona Lisa Re          
Variable Interest Entity [Line Items]          
Ceded premiums written     83,600,000 71,800,000  
Ceded premiums earned     $ 41,200,000 $ 44,600,000