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Property, Plant and Equipment (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022
Property, Plant and Equipment [Line Items] |  |
Total gross property, plant and equipment | $ 8,917.2 | $ 8,374.8
Less accumulated depreciation and depletion | (1,797.9) | (1,576.8)
Property, plant and equipment | 7,119.3 | 6,798.0
Corporate, Non-Segment |  |
Property, Plant and Equipment [Line Items] |  |
Property, Plant and Equipment | 5.7 | 5.7
Construction in progress, gross | 13.6 | 13.7
Total gross property, plant and equipment | 19.3 | 19.4
Less accumulated depreciation and depletion | (1.9) | (1.8)
Property, plant and equipment | $ 17.4 | $ 17.6
Weighted Average | Corporate, Non-Segment |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 10 years | 11 years
Minimum | Corporate, Non-Segment |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 4 years
Maximum | Corporate, Non-Segment |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 23 years
Production, Gas | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 45 years | 45 years
Production, Gas | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 24 years
Production, Gas | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 47 years
Gas transmission | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 58 years | 58 years
Gas transmission | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 32 years
Gas transmission | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 72 years
Gas distribution | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 57 years | 57 years
Gas distribution | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 48 years
Gas distribution | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 61 years
Gas, Storage | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 42 years | 41 years
Gas, Storage | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 36 years
Gas, Storage | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 49 years
General | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 22 years | 23 years
General | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 20 years
General | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 25 years
Electric Utilities |  |
Property, Plant and Equipment [Line Items] |  |
Total plant in service before construction work in progress | $ 4,393.7 | $ 4,190.7
Construction work in progress | 123.1 | 153.0
Property, Plant and Equipment | 4,516.8 | 4,343.7
Less accumulated depreciation and depletion | (1,207.7) | (1,104.1)
Property, plant and equipment | $ 3,309.1 | 3,239.6
Electric Utilities | Wyodak Plant |  |
Property, Plant and Equipment [Line Items] |  |
Depreciation, depletion and amortization, remaining amortization period | 7 years |
Electric Utilities | Production, Electric |  |
Property, Plant and Equipment [Line Items] |  |
Production, processing and storage | $ 1,492.8 | $ 1,482.1
Electric Utilities | Production, Electric | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 40 years | 41 years
Electric Utilities | Production, Electric | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 32 years
Electric Utilities | Production, Electric | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 45 years
Electric Utilities | Electric transmission |  |
Property, Plant and Equipment [Line Items] |  |
Transmission | $ 737.4 | $ 632.9
Electric Utilities | Electric transmission | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 48 years | 48 years
Electric Utilities | Electric transmission | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 42 years
Electric Utilities | Electric transmission | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 51 years
Electric Utilities | Electric distribution |  |
Property, Plant and Equipment [Line Items] |  |
Distribution | $ 1,146.9 | $ 1,082.5
Electric Utilities | Electric distribution | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 47 years | 47 years
Electric Utilities | Electric distribution | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 45 years
Electric Utilities | Electric distribution | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 50 years
Electric Utilities | Integrated Generation |  |
Property, Plant and Equipment [Line Items] |  |
Plant acquisition adjustment | $ 720.0 | $ 713.5
Electric Utilities | Integrated Generation | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 30 years | 31 years
Electric Utilities | Integrated Generation | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 19 years
Electric Utilities | Integrated Generation | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 38 years
Electric Utilities | Plant acquisition adjustment |  |
Property, Plant and Equipment [Line Items] |  |
Plant acquisition adjustment | $ 4.9 | $ 4.9
Electric Utilities | Plant acquisition adjustment | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 32 years | 32 years
Electric Utilities | Plant acquisition adjustment | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 32 years
Electric Utilities | Plant acquisition adjustment | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 32 years
Electric Utilities | General |  |
Property, Plant and Equipment [Line Items] |  |
General | $ 291.7 | $ 274.8
Electric Utilities | General | Weighted Average |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life | 27 years | 27 years
Electric Utilities | General | Minimum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 24 years
Electric Utilities | General | Maximum |  |
Property, Plant and Equipment [Line Items] |  |
Weighted average useful life |  | 28 years
Gas Utilities |  |
Property, Plant and Equipment [Line Items] |  |
Total plant in service before construction work in progress | $ 4,341.9 | $ 3,959.7
Construction in progress, gross | 39.2 | 52.0
Total gross property, plant and equipment | 4,381.1 | 4,011.7
Less accumulated depreciation and depletion | (588.3) | (471.0)
Property, plant and equipment | 3,792.8 | 3,540.7
Gas Utilities | Production, Gas |  |
Property, Plant and Equipment [Line Items] |  |
Production, processing and storage | 21.0 | 17.8
Gas Utilities | Gas transmission |  |
Property, Plant and Equipment [Line Items] |  |
Transmission | 759.5 | 695.4
Gas Utilities | Gas distribution |  |
Property, Plant and Equipment [Line Items] |  |
Distribution | 2,860.0 | 2,620.2
Gas Utilities | Cushion gas - not depreciable |  |
Property, Plant and Equipment [Line Items] |  |
Production, processing and storage | 58.2 | 63.1
Gas Utilities | Gas, Storage |  |
Property, Plant and Equipment [Line Items] |  |
Production, processing and storage | 71.4 | 65.8
Gas Utilities | General |  |
Property, Plant and Equipment [Line Items] |  |
General | $ 571.8 | $ 497.4

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