Revenue Recognition - Narrative (Details) - USD ($)	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue recognized included in contract liability balance at the beginning of the period	$ 4,900,000	$ 3,600,000
Impairment losses recognized on contract costs	0	0
Selling and marketing
Disaggregation of Revenue [Line Items]
Contract costs included in selling and marketing expenses	200,000	$ 200,000
Other Current and Non-current Assets
Disaggregation of Revenue [Line Items]
Contract costs	$ 1,900,000		$ 1,500,000