LONG-TERM DEBT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Long-Term Debt	$ 2,636,278	$ 2,414,256
Debt Instrument, Unamortized Discount	(3,830)	(3,624)
Debt Issuance Costs, Net	(18,955)	(20,691)
Long-term debt, current maturities, net of issuance costs	249,674	14
Long-term Debt, excluding current maturities, net of issuance costs	2,356,038	2,385,286
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	$ (4,300)	(4,800)
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	$ 257,852	287,345
Long-term debt, current maturities, net of issuance costs	$ 30,566	28,956
8.00% Other Long Term Debt
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Long-term Debt, Gross	$ 1,211	1,226
4.960% Unsecured Term Loan Due 2026
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.96%
Long-term Debt, Gross	$ 250,000	$ 0
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.