Goodwill and Intangible Assets - Intangible Assets Subject to Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 3,255	$ 4,993	$ 6,126
Gross Carrying Amount	85,527	103,446
Accumulated Amortization	(81,428)	(94,210)
Total	$ 4,099	$ 9,236
Average Life	6 years	6 years
Completed technology
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1,027	$ 1,766	1,974
Gross Carrying Amount	71,808	83,764
Accumulated Amortization	(70,391)	(80,136)
Total	$ 1,417	$ 3,628
Average Life	5 years	5 years
Customer contracts and relationships
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 2,082	$ 2,927	4,098
Gross Carrying Amount	13,719	19,332
Accumulated Amortization	(11,037)	(13,870)
Total	$ 2,682	$ 5,462
Average Life	9 years	9 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 0	$ 125	25
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	146	175	$ 29
Gross Carrying Amount	0	350
Accumulated Amortization	0	(204)
Total	$ 0	$ 146
Average Life	2 years	2 years