Revenue from Contracts with Customers Disaggregation of Revenue (Tables)

3 Months Ended

Mar. 31, 2023

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue [Table Text Block]

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

	Three Months Ended
	March 31, 2023						March 31, 2022
	Electric		Natural Gas		Total		Electric		Natural Gas		Total
Montana	$	125.5	$	66.9	$	192.4	$	97.0	$	52.3	$	149.3
South Dakota	19.8		19.9		39.7		20.4		19.9		40.3
Nebraska	—		20.5		20.5		—		15.4		15.4
Residential	145.3		107.3		252.6		117.4		87.6		205.0
Montana	112.6		36.3		148.9		86.5		27.1		113.6
South Dakota	25.1		14.3		39.4		27.6		14.5		42.1
Nebraska	—		13.2		13.2		—		9.2		9.2
Commercial	137.7		63.8		201.5		114.1		50.8		164.9
Industrial	11.8		0.7		12.5		9.7		0.6		10.3
Lighting, governmental, irrigation, and interdepartmental	5.3		0.8		6.1		4.5		0.7		5.2
Total Customer Revenues	300.1		172.6		472.7		245.7		139.7		385.4
Other tariff and contract based revenues	21.4		12.3		33.7		20.1		10.0		30.1
Total Revenue from Contracts with Customers	321.5		184.9		506.4		265.8		149.7		415.5
Regulatory amortization and other	(26.2)		(25.7)		(51.9)		5.9		(26.9)		(21.0)
Total Revenues	$	295.3	$	159.2	$	454.5	$	271.7	$	122.8	$	394.5