Goodwill and intangible assets - Intangible Assets Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Acquired Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 66,130	$ 66,130
Impairment	(35,864)	0	$ 0
Accumulated amortization	(15,788)	(11,647)
Intangible assets, net	$ 14,478	$ 54,483
Developed Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average Amortization period in years	17 years	15 years
Gross carrying amount	$ 50,020	$ 50,020
Impairment	(25,198)
Accumulated amortization	(10,344)	(7,636)
Intangible assets, net	$ 14,478	$ 42,384
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average Amortization period in years	0 years	11 years
Gross carrying amount	$ 15,210	$ 15,210
Impairment	(10,541)
Accumulated amortization	(4,669)	(3,461)
Intangible assets, net	$ 0	$ 11,749
Tradenames & Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average Amortization period in years	0 years	3 years
Gross carrying amount	$ 900	$ 900
Impairment	(125)
Accumulated amortization	(775)	(550)
Intangible assets, net	$ 0	$ 350