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Regulatory Matters - NDPSC (Details) - NDPSC - Montana-Dakota Utilities Co. - USD ($) $ in Millions	Nov. 01, 2024	Dec. 13, 2023	Nov. 01, 2023	Sep. 16, 2024
Public Utilities, General Disclosures [Line Items]
Public utilities, annual revenue increase (decrease)				$ 9.4
Public utilities, annual revenue increase (decrease), percentage				6.10%
Natural gas distribution
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount			$ 11.6
Public utilities, requested rate increase (decrease), percentage			7.50%
Public utilities, interim rate increase (decrease), amount		$ 10.1
Public utilities, interim rate increase (decrease), percentage		6.50%
Electric
Public Utilities, General Disclosures [Line Items]
Requested renewable resource cost adjustment rate tariff	$ 18.3
Public utilities, approved rate increase (decrease), amount	$ 2.8

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