Summary of significant accounting policies (Narrative) (Details) - USD ($)	6 Months Ended
	May 31, 2020	Dec. 01, 2019
Likelihood Of Tax Benefit Being Realized Upon Settlement	50.00%
Lease, Practical Expedients, Package [true false]	true
Lease, Practical Expedient, Use of Hindsight [true false]	true
Lease, Practical Expedient, Land Easement [true false]	true
Operating Lease, Right-of-Use Asset	$ 529,000	$ 681,000
Operating Lease, Liability	$ 93,006
ASU 2016-02 [Member]
Operating Lease, Right-of-Use Asset		681,000
ASU 2016-02 [Member] | Restatement Adjustment [Member]
Operating Lease, Right-of-Use Asset		786,000
Operating Lease, Liability		$ 786,000