Share-based payments (Details 7) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based payments
Number of shares outstanding, beginning balance	4,000,000	4,000,000
Number of shares outstanding, ending balance	4,000,000	4,000,000
Number of shares, Exercisable	4,000,000	4,000,000
Weighted-average exercise price per share, beginning balance	$ 2.00	$ 2.00
Weighted-average exercise price per share, ending balance	2.00	2.00
Weighted-average exercise price per share, Exercisable	$ 2.00	$ 2.00