Stock options - Price In Canadian Dollars (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Remaining Life (years)	2 years 11 months 23 days
Canadian Dollar [Member]
Number Outstanding and Exercisable	648	(648)	712
Canadian Dollar [Member] | Price In Canadian Dollars Two Point Four Three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price	$ 2.43
Number Outstanding and Exercisable	648
Weighted Average Remaining Life (years)	7 months 17 days