Goodwill and Intangible Assets Components of Identifiable Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Cost	$ 197,525	$ 191,698
Accumulated Amortization	118,150	109,855
Net Book Value	79,375	81,843
Patents
Finite-Lived Intangible Assets [Line Items]
Cost	9,028	7,808
Accumulated Amortization	7,629	7,486
Net Book Value	1,399	322
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	60,428	60,485
Accumulated Amortization	52,902	51,018
Net Book Value	7,526	9,467
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Cost	9,140	9,142
Accumulated Amortization	4,584	4,204
Net Book Value	4,556	4,938
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	118,929	114,263
Accumulated Amortization	53,035	47,147
Net Book Value	$ 65,894	$ 67,116