v3.26.3
Financing (Details) - USD ($)
$ in Millions
9 Months Ended
Mar. 01, 2026
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Nov. 30, 2025
Debt Instrument [Line Items]          
Repayment of borrowings from long-term debt   $ 550.0 $ 0.0    
Unsecured Debt          
Debt Instrument [Line Items]          
Short-term debt refinanced   $ 600.0      
Unsecured Debt          
Debt Instrument [Line Items]          
Weighted-average interest rates   4.83%   5.03%  
Unsecured Debt | Total Notes And Debentures          
Debt Instrument [Line Items]          
Total notes and debentures   $ 3,300.0   $ 3,800.0  
Unsecured Debt | Boardwalk Pipelines 5.95% Notes Due 2026          
Debt Instrument [Line Items]          
Repayment of borrowings from long-term debt $ 550.0        
Debt interest rate 5.95%        
Unsecured Debt | Boardwalk Pipelines 5.375% Notes due 2036          
Debt Instrument [Line Items]          
Total notes and debentures         $ 550.0
Debt interest rate         5.375%
Line of Credit          
Line of Credit Facility [Abstract]          
Line of credit facility, maximum borrowing capacity   1,000.0      
Line of credit, outstanding borrowings   0.0   0.0  
Available borrowing capacity   983.8      
Letter of Credit          
Line of Credit Facility [Abstract]          
Outstanding Letters of Credit   $ 16.2   $ 0.0