v3.19.3.a.u2

Property, plant and equipment, net (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | $ 893.7 | $ 911.9 |
Less accumulated depreciation | (391.6) | (362.4) |
Total property, plant and equipment, net | 502.1 | 549.5 |
Depreciation expense | 37.6 | 40.0 | $ 83.3
Impairment of property, plant and equipment | 4.0 | 0.0 | $ 67.6
Land |  |  |
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | 6.4 | 5.3 |
Office equipment, machinery and other |  |  |
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | $ 6.5 | 6.0 |
Office equipment, machinery and other | Minimum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 3 years |  |
Office equipment, machinery and other | Maximum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 10 years |  |
Leasehold improvements |  |  |
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | $ 2.1 | 2.1 |
Leasehold improvements | Minimum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 7 years |  |
Leasehold improvements | Maximum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 15 years |  |
Asset retirement obligation. |  |  |
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | $ 23.4 | 24.1 |
Asset retirement obligation. | Minimum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 1 year |  |
Asset retirement obligation. | Maximum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 43 years |  |
Plant in service |  |  |
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | $ 848.1 | $ 874.4 |
Plant in service | Minimum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 1 year |  |
Plant in service | Maximum |  |  |
Property, plant and equipment, net |  |  |
Depreciable Lives | 45 years |  |
Construction in progress |  |  |
Property, plant and equipment, net |  |  |
Property, plant and equipment, gross | $ 7.2 |  |

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