Business Acquisitions - Total Purchase Price and Identifiable Intangible Assets (Details) - USD ($) $ in Thousands				9 Months Ended
	Apr. 30, 2015	Apr. 30, 2015	Apr. 21, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Total Purchase Price
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	26,145	26,145		$ 148,727		$ 122,720
Other non-current assets	52	52
Total assets	57,315	57,315
Current liabilities	7,809	7,809
Non-current 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 purchase price	41,375	41,375
Total purchase price, net of cash received	37,586			$ 25,455	$ 19,749
Mach4 [Member]
Total Purchase Price
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
Goodwill			10,539
Other non-current assets			52
Total assets			26,852
Current liabilities			3,684
Non-current deferred tax liabilities			2,564
Deferred service revenue and gross profit			2,314
Other non-current liabilities			1,056
Total purchase price			17,234
Total purchase price, net of cash received			16,837
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased			7,710
Avantec [Member]
Total Purchase Price
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
Goodwill	15,606	15,606
Other non-current assets	0	0
Total assets	30,463	30,463
Current liabilities	4,125	4,125
Non-current deferred tax liabilities	1,269	1,269
Deferred service revenue and gross profit	928	928
Other non-current liabilities	0	0
Total purchase price	$ 24,141	24,141
Total purchase price, net of cash received		20,749
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased		6,341
Developed technology [Member] | Mach4 [Member]
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased			$ 3,290
Weighted average useful life (in years)			8 years
Trade names [Member] | Mach4 [Member]
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased			$ 850
Weighted average useful life (in years)			6 years
Trade names [Member] | Avantec [Member]
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased		$ 92
Weighted average useful life (in years)		2 years
Customer relationships [Member] | Mach4 [Member]
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased			$ 3,570
Customer relationships [Member] | Avantec [Member]
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased		$ 5,834
Weighted average useful life (in years)		12 years
Backlog [Member] | Avantec [Member]
Identifiable Intangible Assets
Fair value of identifiable intangible assets purchased		$ 415
Weighted average useful life (in years)		2 years
Minimum [Member] | Customer relationships [Member] | Mach4 [Member]
Identifiable Intangible Assets
Weighted average useful life (in years)			11 years
Maximum [Member] | Customer relationships [Member] | Mach4 [Member]
Identifiable Intangible Assets
Weighted average useful life (in years)			12 years