v3.19.3.a.u2

Property, plant and equipment, net - Impairments (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) project
Asset Impairment Charges [Abstract] |  |  |
Impairment of property, plant and equipment | $ 4.0 | $ 0.0 | $ 67.6
Impairment of Ongoing Project | 55.0 |  | 187.1
Calstock |  |  |
Asset Impairment Charges [Abstract] |  |  |
Asset group for testing long-lived assets | 7.8 |  |
Net working capital | 2.3 |  |
Impairment of Ongoing Project | 4.7 |  |
Impairment of intangible assets related to PPAs | 0.7 |  |
Partial impairment of PP&E | 4.0 |  |
Impairment losses related to spare parts inventory | 1.1 |  |
Calstock | Property, Plant and Equipment |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of intangible assets related to PPAs | 4.7 |  |
Calstock | Power Purchase agreements |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of intangible assets related to PPAs | $ 0.8 |  |
Williams Lake |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of property, plant and equipment |  | 0.0 |
Asset group for testing long-lived assets |  | $ 11.4 | $ 40.0
Remaining useful life of the project |  | 20 years | 22 years
Impairment of Ongoing Project |  |  | $ 29.1
Impairment of intangible assets related to PPAs |  |  | 0.6
Williams Lake | Property, Plant and Equipment |  |  |
Asset Impairment Charges [Abstract] |  |  |
Asset group for testing long-lived assets |  |  | 39.4
Partial impairment of PP&E |  |  | 28.5
Williams Lake | Power Purchase agreements |  |  |
Asset Impairment Charges [Abstract] |  |  |
Asset group for testing long-lived assets |  |  | $ 0.6
San Diego Projects |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Number of projects supplying steam | project |  |  | 3
Asset Impairment Charges [Abstract] |  |  |
Impairment of Ongoing Project |  |  | $ 57.3
San Diego Projects | Property, Plant and Equipment |  |  |
Asset Impairment Charges [Abstract] |  |  |
Partial impairment of PP&E |  |  | 39.1
San Diego Projects | Power Purchase agreements |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of intangible assets related to PPAs |  |  | 18.2
Naval Station |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of Ongoing Project |  |  | 22.5
Naval Station | Property, Plant and Equipment |  |  |
Asset Impairment Charges [Abstract] |  |  |
Partial impairment of PP&E |  |  | 12.1
Naval Station | Power Purchase agreements |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of intangible assets related to PPAs |  |  | 10.3
Naval Training Center |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of Ongoing Project |  |  | 13.5
Naval Training Center | Property, Plant and Equipment |  |  |
Asset Impairment Charges [Abstract] |  |  |
Partial impairment of PP&E |  |  | 9.9
Naval Training Center | Power Purchase agreements |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of intangible assets related to PPAs |  |  | 3.6
North Island |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of Ongoing Project |  |  | 21.2
North Island | Property, Plant and Equipment |  |  |
Asset Impairment Charges [Abstract] |  |  |
Partial impairment of PP&E |  |  | 17.0
North Island | Power Purchase agreements |  |  |
Asset Impairment Charges [Abstract] |  |  |
Impairment of intangible assets related to PPAs |  |  | $ 4.2

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