Goodwill and Intangible Assets - Components of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 250,390	$ 210,589
Accumulated Amortization	144,195	127,069
Net Book Value	106,195	83,520
Patents
Finite-Lived Intangible Assets [Line Items]
Cost	9,028	9,028
Accumulated Amortization	7,960	7,729
Net Book Value	1,068	1,299
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	74,747	61,662
Accumulated Amortization	57,734	54,777
Net Book Value	17,013	6,885
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Cost	9,404	9,244
Accumulated Amortization	5,785	4,969
Net Book Value	3,619	4,275
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	157,211	130,655
Accumulated Amortization	72,716	59,594
Net Book Value	$ 84,495	$ 71,061