Acquisitions - Consolidated Business Acquisitions (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
	Nov. 30, 2016	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Sales and results of operations
Sales			$ 340,684	$ 334,677
Operating income (Loss)			(7,004)	(4,101)
Net income (loss)			(9,786)	(2,868)
Estimated acquisition-date fair value of consideration
Compensation expense			1,581	2,314
Purchase price allocation
Goodwill			416,284		$ 415,912
Deltenna
Sales and results of operations
Operating income (Loss)			(100)
Net income (loss)			(100)
Amortization			100
Estimated acquisition-date fair value of consideration
Fair value of consideration transferred		$ 5,300
Cash consideration paid		4,000
Contingent consideration		1,300
Purchase price allocation
Other net liabilities assumed		(300)
Net identifiable assets acquired		1,800
Goodwill		3,500
Net assets acquired		$ 5,300
Weighted average useful life of intangible assets		8 years
Estimated amortization expense related to the intangible assets
2018					300
2019					300
2020					300
2021					300
2022					300
Thereafter					700
Deltenna | Maximum
Estimated acquisition-date fair value of consideration
Contingent consideration		$ 7,300	7,300
Deltenna | Customer relationships
Purchase price allocation
Amortizable intangible assets		1,000
Deltenna | Technology
Purchase price allocation
Amortizable intangible assets		$ 1,100
Vocality
Sales and results of operations
Sales			2,200	100
Operating income (Loss)			100	(1,100)
Net income (loss)			100	(900)
Amortization			200
Acquisition-related expenses			600	800
Estimated acquisition-date fair value of consideration
Compensation expense				$ 400
Fair value of consideration transferred	$ 9,600
Cash consideration paid	9,700
Contingent consideration	300
Cash paid related to compensation expenses	400
Purchase price allocation
Inventory	1,700
Accounts payable and accrued expenses	(400)
Other net liabilities assumed	(500)
Net identifiable assets acquired	5,700
Goodwill	3,900
Net assets acquired	$ 9,600
Weighted average useful life of intangible assets	9 years
Estimated amortization expense related to the intangible assets
2018					800
2019					700
2020					600
2021					600
2022					500
Thereafter					$ 1,300
Vocality | Trade names
Purchase price allocation
Indefinite intangible assets	$ 400
Vocality | Customer relationships
Purchase price allocation
Amortizable intangible assets	2,100
Vocality | Technology
Purchase price allocation
Amortizable intangible assets	$ 2,400
GATR | Maximum
Estimated acquisition-date fair value of consideration
Contingent consideration			7,500
TeraLogics | Maximum | Contract extensions
Estimated acquisition-date fair value of consideration
Contingent consideration			$ 1,000