Derivative Financial Instruments - Open Commodity Derivative Instruments (Details) - bbl bbl in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Canadian crude oil
Derivative [Line Items]
Number of barrels	4	2

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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Period Type:	duration