Goodwill and Intangible Assets - Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 149,351	$ 154,158
Accumulated Amortization	(115,732)	(106,837)
Total	$ 33,619	$ 47,321
Average Life	8 years	8 years
Completed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 84,184	$ 87,820
Accumulated Amortization	(70,368)	(67,769)
Total	$ 13,816	$ 20,051
Average Life	5 years	5 years
Customer contracts and relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 64,592	$ 65,762
Accumulated Amortization	(45,034)	(38,930)
Total	$ 19,558	$ 26,832
Average Life	12 years	12 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 575	$ 576
Accumulated Amortization	(330)	(138)
Total	$ 245	$ 438
Average Life	3 years	3 years