Supplementary Balance Sheet Information - Allowance for Expected Credit Losses Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 4,318	$ 7,146	$ 3,548
Provisions	3,536	3,445	4,600
Reversals of bad debt expense	(2,692)	(6,273)	(1,002)
Balance at end of period	$ 5,162	$ 4,318	$ 7,146