Goodwill and Intangible Assets - Components of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Cost	$ 210,589	$ 191,698
Accumulated Amortization	127,069	109,855
Net Book Value	83,520	81,843
Patents
Finite-Lived Intangible Assets [Line Items]
Cost	9,028	7,808
Accumulated Amortization	7,729	7,486
Net Book Value	1,299	322
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	61,662	60,485
Accumulated Amortization	54,777	51,018
Net Book Value	6,885	9,467
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Cost	9,244	9,142
Accumulated Amortization	4,969	4,204
Net Book Value	4,275	4,938
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	130,655	114,263
Accumulated Amortization	59,594	47,147
Net Book Value	$ 71,061	$ 67,116