Jointly Owned Utility Facilities (Details) $ in Millions	Dec. 31, 2023 USD ($) MW	Sep. 30, 2023 MW
WE | West Riverside
Jointly owned utility facilities
Share of capacity (MW) | MW		100
ER 1 & ER2 | We Power
Jointly owned utility facilities
Joint plant ownership percentage	83.34%
Share of capacity (MW) | MW	1,082.1
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 2,487.4
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(520.0)
Construction work in progress	$ 6.2
Weston Unit 4 | WPS
Jointly owned utility facilities
Joint plant ownership percentage	70.00%
Share of capacity (MW) | MW	384.8
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 613.3
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(227.3)
Construction work in progress	$ 0.5
Columbia Energy Center Units 1 and 2 | WPS
Jointly owned utility facilities
Joint plant ownership percentage	27.50%
Share of capacity (MW) | MW	312.3
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 433.1
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(173.8)
Construction work in progress	$ 3.5
Forward Wind | WPS
Jointly owned utility facilities
Joint plant ownership percentage	44.60%
Share of capacity (MW) | MW	61.5
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 119.3
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(56.8)
Construction work in progress	$ 0.0
Two Creeks | WPS
Jointly owned utility facilities
Joint plant ownership percentage	66.70%
Share of capacity (MW) | MW	100.0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 136.9
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(14.1)
Construction work in progress	$ 0.0
Badger Hollow I | WPS
Jointly owned utility facilities
Joint plant ownership percentage	66.70%
Share of capacity (MW) | MW	100.0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 146.2
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(9.7)
Construction work in progress	$ 0.1
Red Barn | WPS
Jointly owned utility facilities
Joint plant ownership percentage	90.00%
Share of capacity (MW) | MW	82.4
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 150.0
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(3.2)
Construction work in progress	$ 0.0
West Riverside | WE
Jointly owned utility facilities
Joint plant ownership percentage	13.80%
Share of capacity (MW) | MW	84.9
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 108.7
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(11.3)
Construction work in progress	$ 0.9
Badger Hollow II | WE
Jointly owned utility facilities
Joint plant ownership percentage	66.70%
Share of capacity (MW) | MW	100.0
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 170.1
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(0.3)
Construction work in progress	$ 0.1
Koshkonong | WE and WPS
Jointly owned utility facilities
Joint plant ownership percentage	90.00%
Jointly owned utility plant, proportionate ownership share of solar capacity | MW	270
Paris | WE and WPS
Jointly owned utility facilities
Joint plant ownership percentage	90.00%
Construction work in progress	$ 334.3
Jointly owned utility plant, proportionate ownership share of solar capacity | MW	180
Jointly owned utility plant, proportionate ownership share of battery storage | MW	99
Darien | WE and WPS
Jointly owned utility facilities
Joint plant ownership percentage	90.00%
Construction work in progress	$ 220.4
Jointly owned utility plant, proportionate ownership share of solar capacity | MW	225