Stock options (Tables)

12 Months Ended

Dec. 31, 2018

Share-based Payment Arrangement, Noncash Expense [Abstract]

Schedule stock option activity

	2018				2017				2016
	Number of options		Weighted average exercise price		Number of options		Weighted average exercise price		Number of options			Weighted average exercise price
			US$				US$					US$
Outstanding, beginning of year		-		-		-		-		20,692			3.44
Cancelled		-		-		-		-		(20,692	)		(3.44	)
Outstanding, end of year		-		-		-		-		-			-
Exercisable, end of year		-		-		-		-		-			-