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Inventory (Details)
$ in Millions
6 Months Ended
Jun. 30, 2020
USD ($)
Crude oil inventory  
Inventory [Line Items]  
Impairment losses $ 7.2
Long-term linefill inventory  
Inventory [Line Items]  
Impairment losses 1.3
Equipment and materials  
Inventory [Line Items]  
Impairment losses $ 1.0