Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of interest incurred, capitalized and paid
Interest incurred	$ 1,641	$ 2,870	$ 2,608
Less: Capitalized interest	62	399	425
Interest expense - net	1,579	2,471	2,183
Interest paid	$ 1,799	$ 1,436	$ 1,646