Operating Segments and Related Information (Details 4) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	$ 775,468	$ 711,058
BU assets (accounts receivable, inventory, demo assets and goodwill, Net)	1,678,929	1,615,629
Cash and cash equivalents	284,363	512,144	$ 452,138	$ 519,090
Assets held for sale, net	0	2,032
Prepaid expenses and other current assets	67,615	67,413
Property and equipment, net	253,678	247,407
Deferred Income Tax Assets, Net	97,705	100,620
Goodwill	903,461	904,571
Intangible assets, net	140,551	146,845
Unallocated assets from acquisitions	575,079	14,210
Other assets	108,389	74,942
Assets	3,206,309	2,781,242
Government and Defense
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	359,195	307,041
Goodwill	284,649	284,188
Industrial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	263,551	266,457
Goodwill	390,599	391,603
Commercial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	152,722	137,560
Goodwill	$ 228,213	$ 228,780