Supplemental information (Details) - CAD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Increase Decrease In Working Capital [Abstract]
Accounts receivable	$ (94,562)	$ (34,041)
Crude oil inventory	(10,646)	(2,577)
Prepaid expenses	(4,896)	(1,884)
Accounts payable and accrued liabilities	230,567	37,527
Income taxes payable	(1,651)	2,842
Working capital assumed from acquisitions	(58,841)	0
Initial recognition of IFRS 16 liability	(10,483)	0
Foreign exchange	(873)	(795)
Changes in non-cash working capital	48,615	1,072
Changes in non-cash operating working capital	(6,876)	665
Changes in non-cash investing working capital	55,491	407
Changes in non-cash working capital	$ 48,615	$ 1,072

Adjustments for decrease (increase) in inventories to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Inventories; Profit (loss)]

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Adjustments for decrease (increase) in other current assets to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Other current assets; Profit (loss)]

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Adjustments for decrease (increase) in trade and other receivables to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Trade and other receivables; Profit (loss)]

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Adjustments for income tax expense to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

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Adjustments for increase (decrease) in trade and other payables to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Trade and other payables; Profit (loss)]

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The cash inflow (outflow) from the entity's operations before changes in working capital.

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Adjustments for non-cash items to reconcile profit (loss) to net cash flow from (used in) operating activities that the entity does not separately disclose in the same statement or note. [Refer: Profit (loss)]

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Adjustments for foreign exchange losses (gains) to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

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Adjustments for increase (decrease) in working capital through the initial recognition of IFRS 16 liability.

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Increase (decrease) in working capital

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Other adjustments for which cash effects are investing or financing cash flow

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