Restructuring and Exit Costs (Details Textual) ft² in Thousands, $ in Thousands	3 Months Ended		12 Months Ended	13 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2015 ft²
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs	$ 0	$ 57
Lease Obligation Costs
Restructuring Cost and Reserve [Line Items]
Amount of liability	$ 400				$ 500
September 2017 Restructuring Plan | Restructuring and exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs		(57)		$ (1,100)
September 2017 Restructuring Plan | Employee Severance Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs		(45)	$ (1,275)
Reversals of expense		102	27
Cash payments with restructuring plan		423	$ 431
Amount of liability		$ 337			$ 817	$ 0
2015 Consolidation of US Manufacturing Operations | Lease Obligation Costs
Restructuring Cost and Reserve [Line Items]
Square feet of manufacturing facility | ft²							60