Income taxes (Deferred Tax Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Reserves	$ 610	$ 1,152
Net operating loss carryforwards	85,282	83,608
R&D credit carryforwards	9,047	8,593
Depreciation/amortization deferred	16,978	15,884
Other	5,808	6,076
Net deferred taxes before valuation allowance	117,725	115,313
Less: Valuation allowance	(117,725)	(115,313)
Deferred tax assets	$ 0	$ 0