v3.26.1
Debt - Narrative (Details) - USD ($)
$ in Thousands
 1 Months Ended 6 Months Ended
Mar. 31, 2026
Jun. 30, 2026
Jun. 15, 2026
Line of Credit | The 2026 Revolving Credit Facility | Revolving credit facility      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Maximum borrowing capacity   $ 1,250,000  
Line of credit facility, increase limit   $ 500,000  
Line of credit facility, option to extend, period (up to)   2 years  
Consolidated net worth percentage   65.00%  
Net worth percentage, increase adjustment from equity issuances   50.00%  
Ratio of indebtedness to net capital   0.35  
Line of Credit | The 2026 Revolving Credit Facility | Letter of credit      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Maximum borrowing capacity   $ 500,000  
Line of Credit | Senior Notes 2036 And 2056 | Unsecured Debt      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Stockholders' equity threshold triggering required facility exercise $ 2,800,000    
Origination costs   8,000  
Line of Credit | 2036 Senior Notes | Unsecured Debt      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Stated interest rate 6.311%    
Debt instrument, term 10 years    
Pre-capitalized securities, sold by trust $ 500,000    
Debt maximum issuable amount $ 500,000    
Fee percentage 2.066%    
Line of Credit | 2056 Senior Notes | Unsecured Debt      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Stated interest rate 7.28%    
Debt instrument, term 30 years    
Pre-capitalized securities, sold by trust $ 400,000    
Debt maximum issuable amount $ 400,000    
Fee percentage 2.43%    
Line of Credit | Uncommitted Money Market Line Credit Agreement      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Maximum borrowing capacity   500,000  
Minimum cash advance request   100  
Line of Credit | The Revolving Credit Facility Terminating February 2028 | Revolving credit facility      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Line of credit facility, terminated   $ 1,000,000  
Senior Notes | 6.150% Senior Notes due 2037      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Debt face amount     $ 750,000
Stated interest rate   6.15% 6.15%
Senior Notes | 5.170% Senior Notes due 2027      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Debt face amount   $ 400,000  
Stated interest rate   5.17%  
Surplus Notes | 2027 Surplus Notes      
Schedule of Long Term and Short Term Debt Instruments [Line Items]      
Debt face amount   $ 250,000