Operating Segments and Related Information (Details 4) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	$ 754,570		$ 756,425
Cash, cash equivalents and restricted cash	452,138		519,090	$ 397,436	$ 361,349
Assets held for sale, net	0		67,344
Prepaid expenses and other current assets	62,499		44,360
Property and equipment, net	260,200		263,996
Deferred Income Tax Assets, Net	15,924		21,001
Goodwill	918,292		909,811
Intangible assets, net	163,429		168,130
Other assets	76,948	$ 58,864	59,869
Assets	2,704,000		2,810,026
Government and Defense
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	327,722		332,044
Industrial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	277,682		287,439
Commercial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	$ 149,166		$ 136,942