Acquisition and Divestiture Activities (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Apr. 02, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Acquisition of business, net of cash acquired				$ 14,880	$ 0	$ 0
Acquisition of noncontrolling interests				0	(4,100)	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Goodwill				147,480	$ 142,742	$ 141,407
UltraSource [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Acquisition of business, net of cash acquired		$ 13,596
Finite-lived Intangible Assets Acquired		6,500
Goodwill related to acquisitions		$ 4,227		4,227
Business Acquisition, Name of Acquired Entity		Ultrasource, Inc.
Business Acquisition, Effective Date of Acquisition		Feb. 08, 2018
Sonntag [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Acquisition of business, net of cash acquired			$ 5,450
Goodwill related to acquisitions			$ 3,485
Gross purchase price of acquired business							$ 6,750
Business Acquisition, Name of Acquired Entity			Sonntag Electronic GmbH
Business Acquisition, Effective Date of Acquisition			Jan. 01, 2016
EuroPower [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Acquisition of business, net of cash acquired	$ 2,939
Goodwill related to acquisitions	$ 1,068			1,068
Business Acquisition, Name of Acquired Entity	EuroPower Holdings Ltd.
Business Acquisition, Effective Date of Acquisition	Jun. 11, 2018
Bi-Metallix [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Acquisition of business, net of cash acquired				$ 12,000
Business Acquisition, Name of Acquired Entity				Bi-Metallix, Inc.
Business Acquisition, Effective Date of Acquisition				Jan. 03, 2019