Revenue from Contracts with Customers

6 Months Ended

Jun. 30, 2025

Revenue from Contract with Customer [Abstract]

Revenue from Contract with Customer [Text Block]

Revenue from Contracts with Customers

Nature of Goods and Services

We provide retail electric and natural gas services to three primary customer classes. Our largest customer class consists of residential customers, which includes single private dwellings and individual apartments. Our commercial customers consist primarily of main street businesses, and our industrial customers consist primarily of manufacturing and processing businesses that turn raw materials into products.

Electric Segment - Our regulated electric utility business primarily provides generation, transmission, and distribution services to customers in our Montana and South Dakota jurisdictions. We recognize revenue when electricity is delivered to the customer. Payments on our tariff-based sales are generally due 0-30 days after the billing date.

Natural Gas Segment - Our regulated natural gas utility business primarily provides production, storage, transmission, and distribution services to customers in our Montana, South Dakota, and Nebraska jurisdictions. We recognize revenue when natural gas is delivered to the customer. Payments on our tariff-based sales are generally due 0-30 days after the billing date.

Disaggregation of Revenue

The following tables disaggregate our revenue by major source and customer class (in millions):

	Three Months Ended
	June 30, 2025						June 30, 2024
	Electric		Natural Gas		Total		Electric		Natural Gas		Total
Montana	$	81.8	$	18.0	$	99.8	$	86.0	$	18.9	$	104.9
South Dakota	16.2		5.6		21.8		15.4		5.9		21.3
Nebraska	—		4.5		4.5		—		3.8		3.8
Residential	98.0		28.1		126.1		101.4		28.6		130.0
Montana	93.9		10.4		104.3		99.7		10.7		110.4
South Dakota	27.8		3.9		31.7		26.3		3.7		30.0
Nebraska	—		2.4		2.4		—		2.0		2.0
Commercial	121.7		16.7		138.4		126.0		16.4		142.4
Industrial	9.9		0.1		10.0		11.3		0.2		11.5
Lighting, governmental, irrigation, and interdepartmental	9.4		0.3		9.7		8.6		0.3		8.9
Total Retail Revenues	239.0		45.2		284.2		247.3		45.5		292.8
Regulatory Amortization	10.3		5.2		15.5		(10.9)		3.7		(7.2)
Transmission	28.1		—		28.1		22.4		—		22.4
Transportation, wholesale and other	2.1		12.8		14.9		1.3		10.6		11.9
Total Revenues(1)	$	279.5	$	63.2	$	342.7	$	260.1	$	59.8	$	319.9

	Six Months Ended
	June 30, 2025						June 30, 2024
	Electric		Natural Gas		Total		Electric		Natural Gas		Total
Montana	$	196.8	$	69.4	$	266.2	$	203.4	$	67.5	$	270.9
South Dakota	38.5		21.2		59.7		34.7		19.5		54.2
Nebraska	—		17.7		17.7		—		14.3		14.3
Residential	235.3		108.3		343.6		238.1		101.3		339.4
Montana	190.9		37.2		228.1		201.2		35.8		237.0
South Dakota	57.1		15.1		72.2		54.1		13.0		67.1
Nebraska	—		9.8		9.8		—		8.2		8.2
Commercial	248.0		62.1		310.1		255.3		57.0		312.3
Industrial	20.0		0.6		20.6		23.0		0.6		23.6
Lighting, governmental, irrigation, and interdepartmental	14.0		0.8		14.8		13.3		0.9		14.2
Total Retail Revenues	517.3		171.8		689.1		529.7		159.8		689.5
Regulatory Amortization	38.0		(4.2)		33.8		25.5		10.6		36.1
Transmission	54.7		—		54.7		44.8		—		44.8
Transportation, wholesale and other	5.0		26.7		31.7		3.3		21.6		24.9
Total Revenues(1)	$	615.0	$	194.3	$	809.3	$	603.3	$	192.0	$	795.3