Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Valuation allowance - deferred tax assets
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 4,372	$ 3,810	$ 3,291
Charged to costs and expenses	(2,186)	670	529
Charged to Other Accounts	0	0	0
Deductions	0	108	10
Balance at end of period	2,186	4,372	3,810
Reserve for future credit returns and pricing adjustments
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	1,476	2,677	2,560
Charged to costs and expenses	15,477	17,816	12,640
Charged to Other Accounts	0	0	0
Deductions	16,023	19,017	12,523
Balance at end of period	$ 930	$ 1,476	$ 2,677