Goodwill and Intangible Assets - Components of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Cost	$ 386,865	$ 384,611
Accumulated Amortization	144,617	133,443
Net Book Value	242,248	251,168
Patents
Finite-Lived Intangible Assets [Line Items]
Cost	5,302	5,302
Accumulated Amortization	4,702	4,628
Net Book Value	600	674
Completed Technology
Finite-Lived Intangible Assets [Line Items]
Cost	88,819	88,288
Accumulated Amortization	41,548	38,778
Net Book Value	47,271	49,510
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Cost	25,424	25,340
Accumulated Amortization	6,689	5,807
Net Book Value	18,735	19,533
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	267,087	265,450
Accumulated Amortization	91,474	84,047
Net Book Value	175,613	181,403
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Cost	233	231
Accumulated Amortization	204	183
Net Book Value	$ 29	$ 48