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NDPSC (Details 3) - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - USD ($) $ in Millions	Jul. 15, 2021	Jun. 01, 2021
Gas Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 13.5
Pending Rate Case [Member] | Electric | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Total Transmission Cost Adjustment Rider	$ 14.5
Public Utilities, Requested Rate Increase (Decrease), Amount	(1.1)
Transmission Capital Projects Increase (Decrease)	$ 5.1

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Transmission Capital Projects Increase (Decrease)

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Amount of public utility's approved rate increase (decrease) by regulatory agency.

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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