Operating Segments and Related Information (Details 4) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	$ 725,585		$ 756,425
BU assets (accounts receivable, inventory, demo assets and goodwill, Net)	1,629,434
Cash, cash equivalents and restricted cash	507,942		519,090	$ 403,591	$ 361,349
Assets held for sale, net	0		67,344
Prepaid expenses and other current assets	52,307		44,360
Property and equipment, net	252,478		263,996
Deferred Income Tax Assets, Net	22,574		21,001
Goodwill	903,849	$ 909,811	909,811
Intangible assets, net	154,958		168,130
Other assets	85,382	58,864	59,869
Assets	2,705,075		2,810,026
Government and Defense
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	303,170		332,044
Goodwill	290,908	291,229
Industrial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	279,060		287,439
Goodwill	386,753	389,575
Commercial
Segment Reporting, Asset Reconciling Item [Line Items]
BU assets (accounts receivable, inventory and demo assets, Net)	143,355		$ 136,942
Goodwill	$ 226,188	$ 229,007