Financial Instruments - Notional amounts (Details) - Not Designated as Hedging Instrument [Member] - Commodity Contract [Member] - bbl bbl in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Short [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	4,374	3,624	9,108	7,763
Long [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	4,121	3,816	9,025	7,191

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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