Hedge Contracts Hedge Contracts (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Derivatives, Fair Value [Line Items]
Total	$ 120,000	$ 57,000
Derivative [Line Items]
Net gain associated with foreign currency derivative program	(38,000)	378,000	$ 514,000
Forward Sale Contract, Mexican Pesos [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 6,067	$ 2,483,000
Traded exchange rate	19.28	20.18
Value date	Jan. 18, 2018	Jan. 18, 2017
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Forward sale contracts	$ 130,000	$ 57,000
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward sale contracts	$ (10,000)	$ 0