Intangible Assets (Details) - USD ($) $ in Thousands			12 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 123,100
In Process Research and Development			$ 5,602	$ 4,700
Net carrying amount			168,130	168,460
Aggregate amortization expense			27,500	18,400	$ 16,400
2017			23,949
2018			23,028
2019			20,132
2020			18,456
2021			18,119
Armasight, Inc. and Point Grey Research, Inc.
Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			47,400
DVTEL [Member]
Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			27,400
acquired indefinite life intangible asset		27380
Prox Dynamics, AS [Member]
Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 31,400
acquired indefinite life intangible asset	31400000
Acquired identifiable intangibles
Intangible Assets [Line Items]
Acquired identifiable intangibles,Gross			246,069	238,089
Less accumulated amortization			(80,841)	(73,535)
Net carrying amount			165,228	164,554
Aggregate amortization expense			(27,391)	(18,266)	$ (16,275)
Product technology | Acquired identifiable intangibles
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross			$ 123,474	98,895
Weighted average estimated useful life			10 years
Trade name | Acquired identifiable intangibles
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross			$ 73,382	87,013
Weighted average estimated useful life			11 years
Trademarks and tradename portfolios | Acquired identifiable intangibles
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross			$ 9,606	8,160
Weighted average estimated useful life			13 years
Tradename not subject to amortization | Acquired identifiable intangibles
Intangible Assets [Line Items]
acquired indefinite life intangible asset			indefinite
In Process Research and Development | Acquired identifiable intangibles
Intangible Assets [Line Items]
Weighted average estimated useful life			7 years
Trade Secrets | Acquired identifiable intangibles
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross			$ 1,929	1,827
Weighted average estimated useful life			3 years
Patents | Nonacquired intangibles
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross			$ 6,112	6,083
Less accumulated amortization			(3,399)	(2,531)
Net carrying amount			$ 2,713	3,552
Weighted average estimated useful life			7 years
Acquired in-place leases and other | Acquired identifiable intangibles
Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross			$ 456	2,074
Less accumulated amortization			(267)	(1,720)
Net carrying amount			$ 189	354
Acquired in-place leases and other | Nonacquired intangibles
Intangible Assets [Line Items]
Weighted average estimated useful life			7 years
Trade Names [Member] | Prox Dynamics, AS [Member]
Intangible Assets [Line Items]
acquired indefinite life intangible asset	1400
Weighted average estimated useful life	8 years
Trade Names [Member] | Acquired identifiable intangibles
Intangible Assets [Line Items]
Infinite-Lived Intangibles, Gross			$ 32,076	$ 37,494