Other long term obligations - Other liabilities and obligations (Details) - CAD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Deferred gain on sale-leaseback [Roll Forward]
Balance, beginning of year	$ 8,438	$ 7,654
Addition	0	2,262
Amortization of deferred gain on sale-leaseback	(1,845)	(1,478)
Balance, end of year	$ 6,593	$ 8,438

The portion of the gain that will be recorded as income or a reduction in rent expense in future periods less amounts recognized in the current period.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=108788860&loc=d3e50609-112754

Name:	us-gaap_SaleLeasebackTransactionDeferredGainNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant