Mineral properties and development costs - Narrative (Details) - USD ($)			10 Months Ended	12 Months Ended			131 Months Ended	204 Months Ended
	Apr. 10, 2017	Oct. 19, 2011	Nov. 30, 2020	Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2020	Nov. 30, 2020	Feb. 11, 2020	Jan. 11, 2010
Feasibility study (note 6(d))				$ 1,065,000
Mineral property expense				1,545,000	$ 19,211,000	$ 16,490,000
Property, plant and equipment			$ 618,000	618,000			$ 618,000	$ 618,000
Payments received recognized as consideration					31,000,000.0
Feasibility study costs				1,065,000
Cumulative spend								147,000,000
Mineral properties and development costs					30,631,000
Option Agreement to Form a Joint Venture with South32 | South32
Mineral property, fair value of consideration
Mineral properties									30,600,000
Maximum subscription price	$ 150,000,000
Required minimum amount to maintain option in good standing, period	3 years
Option to enter into the 50/50 joint venture, period (in years)	3 years
Percentage of ownership	50.00%
Subscription of options, description	To subscribe for 50% of the joint venture, the Option Agreement provided that South32 must contribute $150 million, plus (i) any amounts Trilogy spends on matched parallel funding to a maximum of $16 million over the three-year period and (ii) $5 million if the option had been exercised between April 1, 2018 and March 31, 2019 or $10 million if the option was exercised between April 1, 2019 and the expiration date of the option, less the amount of the initial funding contributed by South32 (the “Subscription Price”).
Machinery and equipment									620,000
Scenario, Plan | Option Agreement to Form a Joint Venture with South32 | South32
Matched parallel funding on Trilogy spending, maximum amount	$ 16,000,000
Required minimum amount to maintain option in good standing	10,000,000
Amount due if exercised between April 1, 2018 and March 31, 2019	5,000,000
Amount due if exercised between April 1, 2019 and the expiration date	$ 10,000,000
Alaska, USA
Mineral property expense				1,545,000	19,211,000	16,490,000
Mineral properties			30,631,000	30,631,000			30,631,000	30,631,000
Cumulative spend								115,300,000
Cumulative acquisition costs								30,600,000
Mineral properties and development costs					30,631,000	30,587,000
Ambler | Alaska, USA
Mineral property interest percentage										100.00%
Mineral property, fair value of consideration										$ 26,600,000
Net smelter return royalty										1.00%
Purchase price for smelter return royalty (one-time payment)										$ 10,000,000.0
Mineral properties			26,631,000	26,631,000			26,631,000	26,631,000
Mineral properties and development costs					26,631,000	26,587,000
Arctic Project
Feasibility study (note 6(d))			1,100,000	1,500,000
Cost of feasibility study							700,000
Feasibility study costs			1,100,000	1,500,000
Bornite
Payments for mineral property		$ 4,000,000
Net proceeds royalty		15.00%
Minimum purchase amount		$ 0
Bornite | Alaska, USA
Discount on consideration		$ 40,000,000
Mineral properties			$ 4,000,000	$ 4,000,000			$ 4,000,000	$ 4,000,000
Mineral properties and development costs					$ 4,000,000	$ 4,000,000
Bornite | Minimum
Mineral property interest percentage		16.00%
Net smelter return royalty		1.00%
Bornite | Maximum
Mineral property interest percentage		25.00%
Net smelter return royalty		2.50%
Upper Kobuk Mineral Projects | Option Agreement to Form a Joint Venture with South32
Mineral properties									$ 30,600,000