Impairment of Consumer Night Vision Business Assets (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Asset Impairment Charges [Line Items]
Number of products, exiting buisness associated with | item	2
Impairment of Consumer Night Vision Business inventory	$ 2,700	$ 2,690
Other accrued expenses		1,827	$ 719
Impairment of Consumer Night Vision Business tooling	100	$ 76
Contract Manufacturer [Member]
Asset Impairment Charges [Line Items]
Other accrued expenses	$ 1,400