Balance Sheet Components - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Line Items]
Accounts receivable, allowance for credit loss	$ 600	$ 700
Depreciation	23,800	27,300
Impairment of long-lived assets	0	44,930	$ 6,785
Capitalized computer software, net	3,200	5,200
Capitalized computer software, amortization	2,900	2,600
United States
Property, Plant and Equipment [Line Items]
Property and equipment	102,300	102,300
Non-US
Property, Plant and Equipment [Line Items]
Property and equipment	$ 0	$ 200