LONG-TERM DEBT (Tables)

12 Months Ended

Dec. 31, 2025

Long-Term Debt, Unclassified [Abstract]

Schedule of Long-Term Debt Instruments

The table below presents a summary of our long-term debt outstanding for the periods indicated:

		December 31,
	Interest Rate	2025		2024
		(Thousands of dollars)
Senior Notes due:
April 2029	5.100%	$	550,000	$	550,000
May 2030	2.000%	300,000		300,000
September 2032	4.250%	300,000		300,000
February 2044	4.658%	600,000		600,000
November 2048	4.500%	400,000		400,000
Total Senior Notes		2,150,000		2,150,000
Unsecured Term Loan (a)	4.960%	250,000		—
KGSS-I Securitized Utility Tariff Bonds	5.486%	257,852		287,345
Unamortized discounts, net of premiums, on long-term debt (b)		(3,830)		(3,624)
Debt issuance costs (b)		(18,955)		(20,691)
Other	8.000%	1,211		1,226
Total long-term debt, net		2,636,278		2,414,256
Less: current maturities of KGSS-I securitized utility tariff bonds, net		30,566		28,956
Less: current maturities of other long-term debt, net		249,674		14
Noncurrent portion of long-term debt, net		$	2,356,038	$	2,385,286

(a) Bears interest at a variable rate based on Term SOFR, initially set using the 6-month SOFR at closing. The interest rate resets at months six and twelve, each based on the prevailing 6-month Term SOFR and the 1-month Term SOFR, respectively.

(b) Includes issuance costs and discounts for the KGSS-I Securitized Utility Tariff Bonds of $4.3 million and $4.8 million, at December 31, 2025 and December 31, 2024, respectively.