Income taxes, Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Unrecognized tax benefits [Roll Forward]
Unrecognized tax benefits, beginning of period	$ 114	$ 124
Tax positions taken during the current period	27	25
Lapse of statute of limitations	(30)	(35)
Unrecognized tax benefits, end of period	111	114
Accrued interest and penalties related to uncertain tax positions	$ 18	$ 19