Acquisition Activities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Jul. 01, 2017
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Acquisition of business, net of cash acquired			$ 14,880	$ 0
UltraSource [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Purchase price of businesses		$ 13,596
Finite-lived Intangible Assets Acquired		6,500
Goodwill related to acquisitions		$ 4,227
Business Acquisition, Name of Acquired Entity		UltraSource, Inc.
Business Acquisition, Effective Date of Acquisition		Feb. 08, 2018
EuroPower [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Purchase price of businesses	$ 2,949
Goodwill related to acquisitions	$ 1,078
Business Acquisition, Name of Acquired Entity	EuroPower Holdings Ltd.
Business Acquisition, Effective Date of Acquisition	Jun. 11, 2018