Restructuring and Exit Costs (Details Textual) ft² in Thousands	3 Months Ended			6 Months Ended		7 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2015 ft²
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs	$ (78,000)		$ 0	$ (21,000)	$ (997,000)
Lease Obligation Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs	(100,000)	$ (200,000)
Amount of liability	600,000			600,000			$ 700,000
September 2017 Restructuring Plan | Restructuring and exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs				(65,000)		$ (1,200,000)
September 2017 Restructuring Plan | Employee Severance Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs				(45,000)			(1,275,000)
Reversals of expense				110,000			27,000
Cash payments with restructuring plan				689,000			431,000
Amount of liability	63,000			63,000			817,000	$ 0
February 2017 Restructuring Plan | Restructuring and exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			0		(1,000,000)		(900,000)
February 2017 Restructuring Plan | Employee Severance Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs				0			(997,000)
Reversals of expense				0			142,000
Cash payments with restructuring plan			$ 300,000	0	$ 600,000		855,000
Amount of liability	$ 0			$ 0			$ 0	$ 0
2015 Consolidation of US Manufacturing Operations | Lease Obligation Costs
Restructuring Cost and Reserve [Line Items]
Square feet of manufacturing facility | ft²									60