Balance sheet components - Other non-current assets (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Convertible note receivable	$ 3,021
Other non-current assets	4,653	$ 2,823
Other non-current assets	7,674	$ 2,823
Convertible note receivable
Maximum loan offered to borrower	$ 3,000
Interest rate on promissory note	4.00%

Amount of noncurrent assets classified as other.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Name:	us-gaap_OtherAssetsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant