Regulatory matters - MTPSC (Details) - Pending Rate Case - Natural gas distribution - MTPSC - Montana-Dakota Utilities Co. - USD ($) $ in Millions	Oct. 15, 2024	Jul. 15, 2024
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount		$ 9.4
Public utilities, requested rate increase (decrease), percentage		11.10%
Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount	$ 8.0
Public utilities, requested rate increase (decrease), percentage	10.20%