Business Acquisitions (Details textual) - USD ($) $ in Thousands							12 Months Ended
	Oct. 16, 2018	Sep. 10, 2018	Apr. 03, 2018	Mar. 26, 2018	Nov. 30, 2016	Nov. 04, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Business Acquisition [Line Items]
Gain (Loss) on Disposition of Business							$ (13,708)	$ (23,588)	$ 0
Loss on sale of business							(13,708)		0
Goodwill							904,571	909,811	$ 801,406	$ 909,811
Goodwill, Acquired During Period							9,228	96,431
Point Grey Research, Inc. [Member]
Business Acquisition [Line Items]
Cash acquired						$ 2,994
Goodwill						183,678
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent						2,438
Total purchase price						259,161
Identifiable intangible assets						$ 39,800
Prox Dynamics, AS [Member]
Business Acquisition [Line Items]
Cash acquired								11,706
Goodwill								96,431
Total purchase price					$ 134,400			134,387
Goodwill, Acquired During Period								96,431
Net tangible assets					11,300			(900)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles					$ 123,100			$ 31,400
Fishidy [Member]
Business Acquisition [Line Items]
Total purchase price			$ 7,100
Goodwill, Acquired During Period							4,578
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles							$ 3,782
Fishing Hot Spots [Member]
Business Acquisition [Line Items]
Total purchase price				$ 7,100
Acyclica [Member]
Business Acquisition [Line Items]
Total purchase price		$ 10,300
SeaPilot [Member]
Business Acquisition [Line Items]
Total purchase price	$ 4,600