Derivative Instruments, Fair Values Derivatives, Balance Sheet Location (Details) - Foreign Exchange Contract [Member] - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Estimated fair value of the contracts in the consolidated balance sheets [Abstract]
Asset derivatives	$ 83	$ 201
Liability derivatives	272	242
Net fair value	355	443
Prepaid Expenses and Other Current Assets [Member]
Estimated fair value of the contracts in the consolidated balance sheets [Abstract]
Asset derivatives	$ 83	$ 201