Debt (Tables)

12 Months Ended

Dec. 31, 2019

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, 2019			Amount Outstanding at December 31,  2018			Letters of Credit at December 31, 2019			Expiration Date
			(In millions)
Montana-Dakota Utilities Co.	Commercial paper/Revolving credit agreement	(a)	$	175.0		$	118.6	(b)	$	48.5		$	—		12/19/24
Cascade Natural Gas Corporation	Revolving credit agreement		$	100.0	(c)	$	64.6		$	53.8		$	2.2	(d)	6/7/24
Intermountain Gas Company	Revolving credit agreement		$	85.0	(e)	$	24.5		$	56.3		$	1.4	(d)	6/7/24
Centennial Energy Holdings, Inc.	Commercial paper/Revolving credit agreement	(f)	$	600.0		$	104.3	(b)	$	289.6	(b)	$	—		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). There were no amounts outstanding under the revolving credit agreement at December 31, 2019, and $48.5 million was outstanding at December 31, 2018.

(b) Amount outstanding under commercial paper program.

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

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

(e) Certain provisions allow for increased borrowings, up to a maximum of $110.0 million.

(f) 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). 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, 2019		2019		2018
			(In thousands)
Senior Notes due on dates ranging from October 22, 2022 to November 18, 2059	4.45	%	$	1,850,000	$	1,381,000
Commercial paper supported by revolving credit agreements	2.04	%	222,900		338,100
Term Loan Agreement due on September 3, 2032	2.00	%	9,100		209,800
Credit agreements due on June 7, 2024	4.40	%	89,050		110,100
Medium-Term Notes due on dates ranging from September 1, 2020 to March 16, 2029	6.68	%	50,000		50,000
Other notes due on dates ranging from July 15, 2021 to November 30, 2038	4.48	%	29,117		25,229
Less unamortized debt issuance costs			7,010		5,207
Less discount			50		327
Total long-term debt			2,243,107		2,108,695
Less current maturities			16,540		251,854
Net long-term debt			$	2,226,567	$	1,856,841

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, 2019, were as follows:

	2020		2021		2022		2023		2024		Thereafter
	(In thousands)
Long-term debt maturities	$	16,540	$	1,528	$	148,021	$	77,921	$	373,372	$	1,632,785