Debt (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Outstanding credit facilities

The following table summarizes the outstanding revolving credit facilities of the Company's subsidiaries:

Company	Facility	Facility Limit			Amount Outstanding at December 31, 2022		Amount Outstanding at December 31, 2021		Letters of Credit at December 31, 2022			Expiration Date
		(In millions)
Montana-Dakota Utilities Co.	Commercial paper/Revolving credit agreement (a)	$	175.0		$	117.5	$	64.9	$	—		12/19/24
Cascade Natural Gas Corporation	Revolving credit agreement	$	100.0	(b)	$	44.4	$	71.0	$	2.2	(c)	11/30/27
Intermountain Gas Company	Revolving credit agreement	$	100.0	(d)	$	85.6	$	56.5	$	—		10/13/27
Centennial Energy Holdings, Inc.	Commercial paper/Revolving credit agreement (e)	$	600.0		$	298.0	$	385.4	$	—		12/19/24

(a)The commercial paper program is supported by a revolving credit agreement with various banks (provisions allow for increased borrowings, at the option of Montana-Dakota on stated conditions, up to a maximum of $225.0 million). At December 31, 2022 and 2021, there were no amounts outstanding under the revolving credit agreement.

(b)Certain provisions allow for increased borrowings, up to a maximum of $125.0 million.

(c)Outstanding letter(s) of credit reduce the amount available under the credit agreement.

(d)Certain provisions allow for increased borrowings, up to a maximum of $125.0 million.

(e)The commercial paper program is supported by a revolving credit agreement with various banks (provisions allow for increased borrowings, at the option of Centennial on stated conditions, up to a maximum of $700.0 million). At December 31, 2022 and 2021, there were no amounts outstanding under the revolving credit agreement.

Long term debt outstanding

Long-term debt outstanding was as follows:

	Weighted Average Interest Rate at December 31, 2022		2022		2021
			(In thousands)
Senior Notes due on dates ranging from May 15, 2023 to June 15, 2062	4.32	%	$	2,258,500	$	2,125,000
Commercial paper supported by revolving credit agreements	5.13	%	415,500		450,300
Credit agreements due on October 13, 2027 and November 30, 2027	6.31	%	130,000		127,500
Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029	7.32	%	35,000		35,000
Term Loan Agreement due on September 3, 2032	3.64	%	7,000		7,700
Other notes due on dates ranging from March 1, 2024 to January 1, 2061	1.00	%	2,253		2,564
Less unamortized debt issuance costs			6,542		6,090
Less discount			286		74
Total long-term debt			2,841,425		2,741,900
Less current maturities			78,031		148,053
Net long-term debt			$	2,763,394	$	2,593,847

Schedule of debt maturities

Long-term debt maturities, which excludes unamortized debt issuance costs and discount, for the five years and thereafter following December 31, 2022, were as follows:

	2023		2024		2025		2026		2027		Thereafter
	(In thousands)
Long-term debt maturities	$	78,031	$	476,923	$	177,802	$	140,802	$	230,802	$	1,743,893