Regulatory matters - WUTC (Details) - Natural gas distribution - WUTC - Cascade Natural Gas $ in Millions	Mar. 29, 2024 USD ($)
Pending Rate Case, Multi-Year, Year One
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount	$ 43.8
Public utilities, requested rate increase (decrease), percentage	11.60%
Pending Rate Case, Multi-Year, Year Two
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount	$ 11.7
Public utilities, requested rate increase (decrease), percentage	2.80%