Financial instruments (Details 18) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Single series bond Four [Member] | Interest payment [Member]
Financial instruments [Line Items]
Repayments of bonds, notes and debentures	$ 10,938	$ 10,938	$ 10,938