Balance sheet components - Accrued expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Professional services fees payable	$ 6,163	$ 5,057
Other accrued expenses	9,779	1,380
Accrued expenses	$ 15,942	$ 6,437

Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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Name:	us-gaap_OtherAccruedLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant