Operating Segments and Related Information (Details 4) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	$ 758,168	$ 711,058
BU assets (accounts receivable, inventory, demo assets and goodwill, Net)	2,112,963	1,615,629
Cash and cash equivalents	295,391	512,144	$ 593,335	$ 519,090
Prepaid expenses and other current assets	63,623	69,445
Property and equipment, net	253,338	247,407
Deferred Income Tax Assets, Net	101,211	100,620
Goodwill	1,354,795	904,571
Intangible assets, net	262,095	146,845
Other assets	109,259	89,152
Assets	3,197,880	2,781,242
Government and Defense
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	350,020	307,041
Goodwill	719,082	284,188
Industrial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	268,217	266,457
Goodwill	403,225	391,603
Commercial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	139,931	137,560
Goodwill	$ 232,488	$ 228,780