v3.26.3
VARIABLE INTEREST ENTITIES (Details)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2026
USD ($)
account
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
account
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Variable Interest Entity [Line Items]          
Number of segregated accounts | account 4   4    
Assets $ 54,831,196,000   $ 54,831,196,000   $ 53,800,390,000
Liabilities 36,044,895,000   36,044,895,000   34,589,641,000
Investments 36,191,038,000   36,191,038,000   36,073,209,000
Other assets 452,618,000   452,618,000   328,087,000
Reserve for claims and claim expenses (Note 6) 22,294,195,000 $ 22,712,860,000 22,294,195,000 $ 22,712,860,000 22,302,345,000
Other liabilities 662,632,000   662,632,000   856,302,000
Investments in other ventures, under equity method 162,677,000   162,677,000   121,871,000
Ceded premiums written 438,531,000 265,824,000 1,956,572,000 1,628,708,000  
Ceded premiums earned 559,669,000 $ 464,714,000 1,503,746,000 1,300,284,000  
Variable Interest Entity, Primary Beneficiary | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Assets 462,200,000   462,200,000   653,000,000.0
Liabilities 461,300,000   461,300,000   652,100,000
Investments 391,000,000.0   391,000,000.0   526,800,000
Other assets 71,200,000   71,200,000   126,200,000
Reserve for claims and claim expenses (Note 6) 239,500,000   239,500,000   305,800,000
Other liabilities 221,900,000   221,900,000   346,300,000
Net assets 7,100,000   7,100,000   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     234,900,000 230,500,000  
Net assets 115,400,000   115,400,000   $ 264,800,000
Variable Interest Entity, Primary Beneficiary | RenaissanceRe Holdings Ltd. | Upsilon RFO Re Ltd.          
Variable Interest Entity [Line Items]          
Payments of capital distribution     $ 30,500,000 27,900,000  
Variable interest entity, ownership percentage     12.30%   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     $ 23,600,000 29,500,000  
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Diversified Fund          
Variable Interest Entity [Line Items]          
Investments in other ventures, under equity method 100,000   100,000   $ 400,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Fund Ltd.          
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 1,000,000.0   1,000,000.0   2,200,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Diversified Fund          
Variable Interest Entity [Line Items]          
Assets 185,800,000   185,800,000   278,400,000
Liabilities 105,100,000   105,100,000   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 85,500,000   85,500,000   254,700,000
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Upsilon Fund Ltd.          
Variable Interest Entity [Line Items]          
Assets 425,500,000   425,500,000   454,600,000
Liabilities 1,100,000   1,100,000   700,000
Variable Interest Entity, Not Primary Beneficiary | Mona Lisa Re          
Variable Interest Entity [Line Items]          
Assets 920,800,000   920,800,000   1,100,000,000
Liabilities 920,800,000   920,800,000   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 3,000,000.0   3,000,000.0   3,400,000
Variable Interest Entity, Not Primary Beneficiary | AlphaCat Managers Ltd          
Variable Interest Entity [Line Items]          
Assets 331,100,000   331,100,000   1,100,000,000
Liabilities 107,000,000.0   107,000,000.0   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     300,000 300,000  
Variable Interest Entity, Not Primary Beneficiary | RenaissanceRe Holdings Ltd. | RenaissanceRe Upsilon Fund Ltd.          
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 $ 101,000,000.0   101,000,000.0   $ 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     186,000,000.0 207,800,000  
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 | RenaissanceRe Upsilon Fund Ltd.          
Variable Interest Entity [Line Items]          
Payments of capital distribution     196,600,000    
Payments of dividends     10,800,000    
Variable Interest Entity, Not Primary Beneficiary | Third Party Investor | RenaissanceRe Upsilon Fund Ltd. | Preference shares          
Variable Interest Entity [Line Items]          
Payments to acquire Interest in subsidiaries and affiliates     150,000,000.0    
Variable Interest Entity, Not Primary Beneficiary | Renaissance Reinsurance Ltd. | Mona Lisa Re          
Variable Interest Entity [Line Items]          
Ceded premiums written     83,700,000 70,200,000  
Ceded premiums earned     $ 62,400,000 $ 61,700,000