Income taxes, Valuation allowance on deferred tax assets (Details) - Foreign Net Operating Loss Carryforwards [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation allowance [Roll Forward]
Balance, beginning of period	$ 390	$ 328	$ 423
Additions charged to income tax provision	54	62	67
Reductions credited to income tax provision	0	0	(162)
Balance, end of period	$ 444	$ 390	$ 328