SDPUC (Details 3) - Subsequent Event [Member] - Electricity [Member] - SDPUC [Member] - Montana-Dakota Utilities Co. [Member]	May 01, 2020 USD ($)
Public Utilities, General Disclosures [Line Items]
Total Transmission Cost Adjustment Rider	$ 764,000
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (15,000)
Public Utilities, Approved Rate Increase (Decrease), Percentage	(1.90%)
Transmission Capital Projects Increase (Decrease)	$ 87,000
Electric Rate Proceeding [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	242,000
Total Infrastructure Rider	$ 1,300,000