v3.26.1
Credit Facilities and Long-Term Debt - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 01, 2021
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Jun. 13, 2025
Oct. 31, 2024
Oct. 24, 2023
Feb. 07, 2023
Dec. 29, 2021
Nov. 05, 2021
Apr. 01, 2021
Nov. 03, 2020
Feb. 11, 2019
Line of Credit Facility [Line Items]                          
Credit facilities, unutilized capacity   $ 798,000,000                      
Revolving credit facility, credit agreement maximum limit $ 300,000,000.0                        
Line of credit facility Increasable capacity $ 100,000,000.0                        
Minimum consolidated tangible net worth under credit facility   $ 2,019,600,000                      
Percentage of consolidated net income   25.00%                      
Percentage of aggregate net cash proceeds from the issuance of capital stock   25.00%                      
Percentage of consolidated leverage ratio permitted   35.00%                      
Debt Instrument, Interest Rate, Stated Percentage         5.75%                
AUL | Lloyd's                          
Line of Credit Facility [Line Items]                          
Letter of Credit to Support Funds at Lloyd's             $ 430,000,000.0            
Funds at Lloyd's Facility Agreement           $ 25,000,000.0              
Funds at Lloyd's Amended Facility Agreement           $ 60,000,000.0              
AUL | Lloyd's | Maximum                          
Line of Credit Facility [Line Items]                          
Letter of Credit to Support Funds at Lloyd's                       $ 235,000,000.0  
Bermuda | Natixis                          
Line of Credit Facility [Line Items]                          
Revolving credit facility, credit agreement maximum limit                   $ 100,000,000.0      
Bermuda | HSBC Bank USA, National Association                          
Line of Credit Facility [Line Items]                          
Revolving credit facility, credit agreement maximum limit                 $ 75,000,000.0        
Aspen Specialty | Federal Home Loan Bank of Boston                          
Line of Credit Facility [Line Items]                          
Revolving credit facility, credit agreement maximum limit                     $ 269,000,000    
Percentage limit of pledged assets permitted to secure debt obligations                     15.00%    
AAIC | Federal Home Loan Bank of Boston                          
Line of Credit Facility [Line Items]                          
Revolving credit facility, credit agreement maximum limit                     $ 230,000,000    
Percentage limit of pledged assets permitted to secure debt obligations                     10.00%    
Letters of credit / guarantees | Aspen UK | Aspen European                          
Line of Credit Facility [Line Items]                          
Revolving credit facility, credit agreement maximum limit               $ 100,000,000.0         $ 100,000,000.0
Secured and unsecured financing facilities                          
Line of Credit Facility [Line Items]                          
Long-term line of credit   $ 1,400,000,000                      
Senior Notes                          
Line of Credit Facility [Line Items]                          
Loans issued         $ 300,000,000.0                
Interest Expense   $ 17,400,000 $ 20,500,000 $ 15,600,000