v3.26.1
LONG-TERM DEBT (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2026
Feb. 10, 2026
Dec. 31, 2025
Debt Instrument [Line Items]      
Long-Term Debt $ 2,621,522   $ 2,636,278
Debt Instrument, Unamortized Discount (3,883)   (3,830)
Debt Issuance Costs, Net (18,298)   (18,955)
Long-term debt, current maturities, net of issuance costs 249,798   249,674
Long-term Debt, excluding current maturities, net of issuance costs 2,340,320   2,356,038
Debt Instrument, Covenant Compliance, Default Provision, Indebtnedness Threshold $ 100,000    
Debt Instrument, Covenant Compliance, Default Provision, Debt Holders 25.00%    
Debt Instrument, Redemption Price, Percentage 100.00%    
Kansas Gas Service Securitization I LLC      
Debt Instrument [Line Items]      
Debt Issuance Costs, Net $ (4,100)   (4,300)
5.10% Senior Unsecured Notes Due 2029 [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.10%    
Long-term Debt, Gross $ 550,000   550,000
2.00% Senior Unsecured Notes Due 2030      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.00%    
Long-term Debt, Gross $ 300,000   300,000
4.25% Senior Unsecured Notes Due 2032      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 4.25%    
Long-term Debt, Gross $ 300,000   300,000
4.658% Senior Unsecured Notes Due 2044      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 4.658%    
Long-term Debt, Gross $ 600,000   600,000
4.50% Senior Unsecured Notes Due 2048      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 4.50%    
Long-term Debt, Gross $ 400,000   400,000
Total Senior Unsecured Notes      
Debt Instrument [Line Items]      
Long-term Debt, Gross $ 2,150,000   2,150,000
5.486% KGSS-I Securitized Utility Tariff Bonds Due 2032      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.486%    
Long-term Debt, Gross $ 242,496   257,852
Long-term debt, current maturities, net of issuance costs $ 31,404   30,566
8.00% Other Long Term Debt      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 8.00%    
Long-term Debt, Gross $ 1,207   1,211
4.960% Unsecured Term Loan Due 2026      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 4.48% 4.96%  
Long-term Debt, Gross $ 250,000   $ 250,000
Debt Instrument, Interest Rate Terms The loan bears interest at a variable rate based on Term SOFR, initially set using the 6-month Term SOFR at closing, plus a 90 bps spread as specified in the agreement. The interest rate resets automatically at months six and twelve, each based on the prevailing 6-month Term SOFR plus a spread of 90 bps, and 1-month Term SOFR plus a spread of 90 bps, respectively, until the term loan matures in September 2026.    
Debt Instrument, Reference Rate 3.58%