Share capital - Common shares issued and outstanding (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended	12 Months Ended
	Apr. 20, 2018	Aug. 31, 2019	Aug. 31, 2018	May 31, 2018	Aug. 31, 2019	Nov. 30, 2018
Bought deal financing				$ 28,750
Share issuance costs			$ 14	$ (1,819)
NovaGold DSU conversion			0
Deferred share units (Shares)					182,132
Deferred share units					189,000
Exercise of warrants		$ 9,913
Number of shares		138,905,097			138,905,097
Ascribed value		$ 176,970			$ 176,970
Share capital [Member]
Number of shares					131,585,612	105,684,523
Ascribed value					$ 164,069	$ 136,525
Bought deal financing (Shares)	24,784,482			24,784,482		24,784,482
Bought deal financing	$ 28,700			$ 28,750		$ 28,750
Share issuance costs			$ 14	$ (1,819)		$ (1,805)
Exercise of options (shares)					203,112	315,148
Exercise of options					$ 122	$ 140
Restricted share units (Shares)					412,501	800,000
Restricted share units					$ 424	$ 457
NovaGold DSU conversion (Shares)			1,020			1,459
NovaGold DSU conversion			$ 2			$ 2
Exercise of warrants		$ 12,166			$ 12,166
Exercise of warrants (Shares)		6,521,740			6,521,740
Number of shares						131,585,612
Ascribed value						$ 164,069