Acquisitions (Details) - USD ($) $ in Thousands					3 Months Ended			6 Months Ended		12 Months Ended
	Nov. 30, 2016	Feb. 02, 2016	Dec. 21, 2015	Nov. 04, 2015	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Sep. 30, 2015	Sep. 30, 2016
Acquisitions
Net sales					$ 343,709		$ 366,024	$ 678,386	$ 679,837
Operating income (Loss)					(2,072)		(9,086)	(6,173)	(17,163)
Net income (loss)					461		10,144	(2,407)	4,730
Compensation expense					1,043		1,970	3,357	4,088
Change in fair value of contingent consideration					(880)		(897)	(2,194)	(1,706)
Amortization of purchased intangibles					7,873		8,499	17,228	14,954
Contingent consideration paid								1,988	1,679
Purchase price allocation
Goodwill					409,091			409,091				$ 406,946
Selling, general and administrative
Acquisitions
Compensation expense					935		1,744	3,074	3,544
Vocality
Acquisitions
Net sales					700			800
Operating income (Loss)					(500)			(1,600)
Net income (loss)					(600)			(1,500)
Amortization					200			200
Acquisition-related expenses					400			1,200
Transaction and acquisition related costs					400			1,200
Fair value of consideration transferred	$ 9,600
Cash consideration paid	8,900
Contingent consideration	1,100
Cash paid related to compensation expenses								400
Purchase price allocation
Inventory	1,700
Accounts payable and accrued expenses	(400)
Other net liabilities assumed	(200)
Net identifiable assets acquired	6,000
Goodwill	3,600
Net assets acquired	$ 9,600
Weighted average useful life of intangible assets	9 years
Estimated amortization expense related to the intangible assets
2017												600
2018												800
2019												700
2020												600
2021												500
Thereafter												1,700
Vocality | Selling, general and administrative
Acquisitions
Compensation expense						$ 400
Vocality | Customer relationships
Purchase price allocation
Amortizable intangible assets	$ 2,100
Vocality | Technology
Purchase price allocation
Amortizable intangible assets	2,400
Vocality | Corporate trade names
Purchase price allocation
Amortizable intangible assets	$ 400
GATR
Acquisitions
Net sales					8,900		9,300	27,400	9,300
Operating income (Loss)					(4,800)		(20,700)	(5,300)	(20,700)
Net income (loss)					(2,900)		(18,300)	(3,200)	(18,300)
Amortization					3,000		2,400	6,600	2,400
Gains (losses) for changes in fair value of contingent consideration					1,300		(100)	1,700	(100)
Acquisition-related expenses							18,800	800	19,400
Transaction and acquisition related costs							18,800	800	19,400
Fair value of consideration transferred		$ 220,500
Cash consideration paid		236,100
Contingent consideration		2,500
Cash paid related to compensation expenses		$ 18,100						15,400
Period for contingent consideration contracts		12 months
Purchase price allocation
Accounts receivable		$ 10,600
Inventory		3,400
Income tax receivable		5,100
Accounts payable and accrued expenses		(2,400)
Tax liabilities		(23,800)
Net identifiable assets acquired		64,600
Goodwill		155,900
Net assets acquired		$ 220,500
Weighted average useful life of intangible assets		9 years
Estimated amortization expense related to the intangible assets
2017												12,700
2018												11,100
2019												9,800
2020												8,300
2021												6,900
Thereafter												13,200
GATR | Maximum
Acquisitions
Contingent consideration		$ 7,500
GATR | Selling, general and administrative
Acquisitions
Compensation expense								18,500	18,500
GATR | Customer relationships
Purchase price allocation
Amortizable intangible assets		51,700
GATR | Backlog
Purchase price allocation
Amortizable intangible assets		3,400
GATR | Technology
Purchase price allocation
Amortizable intangible assets		10,700
GATR | Non-compete agreements
Purchase price allocation
Amortizable intangible assets		1,200
GATR | Corporate trade names
Purchase price allocation
Amortizable intangible assets		$ 4,700
TeraLogics
Acquisitions
Net sales					4,800		3,800	11,000	3,800
Operating income (Loss)					(200)		(300)	(200)	(2,000)
Net income (loss)					(100)		(200)	(100)	(1,200)
Amortization					800		1,000	1,800	1,000
Gains (losses) for changes in fair value of contingent consideration					(300)		100	(200)	100
Acquisition-related expenses							500	100	2,200
Transaction and acquisition related costs							500	100	2,200
Compensation expense											$ 1,300
Change in fair value of contingent consideration								3,200
Fair value of consideration transferred			$ 33,900
Cash consideration paid			28,900
Contingent consideration			5,000
Contingent consideration paid										$ 32,400
Purchase price allocation
Accounts receivable			1,400
Accounts payable and accrued expenses			(500)
Other net liabilities assumed			(100)
Net identifiable assets acquired			15,700
Goodwill			18,200
Net assets acquired			$ 33,900
Weighted average useful life of intangible assets			7 years
Estimated amortization expense related to the intangible assets
2017												3,500
2018												2,800
2019												2,100
2020												1,400
2021												800
Thereafter												$ 1,400
TeraLogics | Maximum
Acquisitions
Contingent consideration			$ 9,000
TeraLogics | Maximum | Revenue thresholds
Acquisitions
Contingent consideration			6,000
TeraLogics | Maximum | Contract extensions
Acquisitions
Contingent consideration			3,000
TeraLogics | Customer relationships
Purchase price allocation
Amortizable intangible assets			6,700
TeraLogics | Backlog
Purchase price allocation
Amortizable intangible assets			5,600
TeraLogics | Software.
Purchase price allocation
Amortizable intangible assets			2,500
TeraLogics | Non-compete agreements
Purchase price allocation
Amortizable intangible assets			$ 100
H4 Global
Acquisitions
Net sales					900		600	1,600	600
Operating income (Loss)					(100)		100	(300)
Net income (loss)								(200)
Amortization					$ 100			100
Gains (losses) for changes in fair value of contingent consideration							$ 200	$ 100	200
Acquisition-related expenses									100
Transaction and acquisition related costs									$ 100
Fair value of consideration transferred				$ 1,900
Cash consideration paid				900
Contingent consideration				$ 1,000
Period for contingent consideration contracts				5 years
Purchase price allocation
Goodwill				$ 1,900
H4 Global | Maximum
Acquisitions
Contingent consideration				$ 4,100