Revenue from Contract with Customer - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue recognized included in contract liability balance at the beginning of the period	$ 9,100,000	$ 3,900,000
Impairment losses recognized in capitalized contract costs	0	0
Selling and marketing
Disaggregation of Revenue [Line Items]
Amortization of capitalized contract costs	1,200,000	800,000
Other current and non-current assets
Disaggregation of Revenue [Line Items]
Capitalized contract costs	$ 2,300,000	$ 1,500,000