Goodwill and Intangible Assets - Components of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 198,918	$ 158,300
Accumulated Amortization	98,962	74,796
Net Book Value	99,956	83,504
Patents
Finite-Lived Intangible Assets [Line Items]
Cost	5,302	5,302
Accumulated Amortization	4,325	4,019
Net Book Value	977	1,283
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	44,829	31,264
Accumulated Amortization	28,934	24,379
Net Book Value	15,895	6,885
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Cost	6,298	6,138
Accumulated Amortization	2,953	1,863
Net Book Value	3,345	4,275
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	142,489	115,596
Accumulated Amortization	62,750	44,535
Net Book Value	$ 79,739	$ 71,061