Income taxes - Losses Expiry (Details) $ in Thousands	Nov. 30, 2020 USD ($)
CA
Non-capital losses	$ 46,965
Alaska, USA
Operating losses	121,494
2021 \| Alaska, USA
Operating losses	1
2022 \| Alaska, USA
Operating losses	366
2023 \| Alaska, USA
Operating losses	960
2024 \| Alaska, USA
Operating losses	569
Thereafter \| CA
Non-capital losses	46,965
Thereafter \| Alaska, USA
Operating losses	$ 119,598

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

Name:	us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant