Goodwill and Other Intangible Assets - Summary of Gross Carrying Amounts and Accumulated Amortization of Intangible Assets by Major Class (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2021	Sep. 30, 2020
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 201,758	$ 201,170
Accumulated Amortization	(166,222)	(155,554)
Net Carrying Amount	35,536	45,616
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	110,839	110,512
Accumulated Amortization	(82,562)	(75,915)
Net Carrying Amount	$ 28,277	$ 34,597
Weighted Average Remaining Life (Years)	2 years 7 months 6 days	3 years
Technology and Patents
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 90,919	$ 90,658
Accumulated Amortization	(83,660)	(79,639)
Net Carrying Amount	$ 7,259	$ 11,019
Weighted Average Remaining Life (Years)	1 year 2 months 12 days	1 year 7 months 6 days