Goodwill and Intangible Assets - Components of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Cost	$ 386,716	$ 198,918
Accumulated Amortization	115,923	98,962
Net Book Value	270,793	99,956
Patents
Finite-Lived Intangible Assets [Line Items]
Cost	5,302	5,302
Accumulated Amortization	4,477	4,325
Net Book Value	825	977
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	88,724	44,829
Accumulated Amortization	33,592	28,934
Net Book Value	55,132	15,895
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Cost	25,318	6,298
Accumulated Amortization	4,225	2,953
Net Book Value	21,093	3,345
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	267,372	142,489
Accumulated Amortization	73,629	62,750
Net Book Value	$ 193,743	$ 79,739