NDPSC (Details 2) - Electricity [Member] - Montana-Dakota Utilities Co. [Member] - NDPSC [Member] - USD ($)	Mar. 01, 2020	Oct. 28, 2019
Public Utilities, General Disclosures [Line Items]
Total Transmission Cost Adjustment Rider		$ 9,200,000
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 600,000
Public utilities, approved rate increase (decrease), percentage		7.20%
Transmission Capital Projects Increase (Decrease)		$ 1,500,000
Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (800,000)
Renewable Resource Cost Adjustment Rate Tariff	$ 14,700,000