Business Combinations - Total Purchase Price and Identifiable Intangible Assets (Details) - USD ($) $ in Thousands				12 Months Ended
	Apr. 30, 2015	Apr. 30, 2015	Apr. 21, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill				$ 327,724	$ 147,906	$ 122,720
Total purchase price, net of cash received				312,158	25,507	$ 20,723
Aesynt
Business Acquisition [Line Items]
Cash				8,164
Accounts receivable				43,312
Inventory				19,021
Other current assets				3,787
Total current assets				74,284
Property and equipment				10,389
Intangibles				123,700
Goodwill				163,599
Other non-current assets				968
Total assets				372,940
Current liabilities				26,753
Deferred revenue, net				25,512
Long-term deferred tax liabilities				38,622
Other non-current liabilities				2,431
Total liabilities				93,318
Total purchase price				279,622
Total purchase price, net of cash received				271,500
Ateb
Business Acquisition [Line Items]
Cash				902
Accounts receivable				7,905
Inventory				225
Other current assets				1,239
Total current assets				10,271
Property and equipment				2,447
Intangibles				12,500
Goodwill				20,832
Other non-current assets				1,009
Total assets				47,059
Current liabilities				2,314
Deferred revenue, net				2,776
Long-term deferred tax liabilities				0
Other non-current liabilities				367
Total liabilities				5,457
Total purchase price				41,602
Total purchase price, net of cash received				40,700
Aesynt and Ateb
Business Acquisition [Line Items]
Cash				9,066
Accounts receivable				51,217
Inventory				19,246
Other current assets				5,026
Total current assets				84,555
Property and equipment				12,836
Intangibles				136,200
Goodwill				184,431
Other non-current assets				1,977
Total assets				419,999
Current liabilities				29,067
Deferred revenue, net				28,288
Long-term deferred tax liabilities				38,622
Other non-current liabilities				2,798
Total liabilities				98,775
Total purchase price				321,224
Total purchase price, net of cash received				$ 312,158
Mach4
Business Acquisition [Line Items]
Cash			$ 397
Accounts receivable			3,743
Inventory			3,580
Deferred tax assets and other current assets			368
Total current assets			8,088
Property and equipment			463
Intangibles			7,710		7,710
Goodwill			10,591
Other non-current assets			52
Total assets			26,904
Current liabilities			3,684
Long-term deferred tax liabilities			2,564
Deferred service revenue and gross profit			2,314
Other non-current liabilities			1,056
Total liabilities			9,618
Total purchase price			17,286
Total purchase price, net of cash received			$ 16,889
Avantec
Business Acquisition [Line Items]
Cash	$ 3,392	$ 3,392
Accounts receivable	3,607	3,607
Inventory	1,428	1,428
Deferred tax assets and other current assets	89	89
Total current assets	8,516	8,516
Property and equipment	0	0
Intangibles	6,341	6,341			$ 6,341
Goodwill	15,606	15,606
Other non-current assets	0	0
Total assets	30,463	30,463
Current liabilities	4,125	4,125
Long-term deferred tax liabilities	1,269	1,269
Deferred service revenue and gross profit	928	928
Other non-current liabilities	0	0
Total liabilities	6,322	6,322
Total purchase price	24,141	24,141
Total purchase price, net of cash received		20,749
2015 Acquisitions Mach4 and Avantec [Member]
Business Acquisition [Line Items]
Cash	3,789	3,789
Accounts receivable	7,350	7,350
Inventory	5,008	5,008
Deferred tax assets and other current assets	457	457
Total current assets	16,604	16,604
Property and equipment	463	463
Intangibles	14,051	14,051
Goodwill	26,197	26,197
Other non-current assets	52	52
Total assets	57,367	57,367
Current liabilities	7,809	7,809
Long-term deferred tax liabilities	3,833	3,833
Deferred service revenue and gross profit	3,242	3,242
Other non-current liabilities	1,056	1,056
Total liabilities	15,940	15,940
Total purchase price	41,427	$ 41,427
Total purchase price, net of cash received	$ 37,638