Debt - Convertible Senior Notes Due 2025 (Details) $ / shares in Units, $ in Thousands, shares in Millions			1 Months Ended	12 Months Ended
	May 01, 2025 USD ($)	May 14, 2018	Apr. 30, 2025 USD ($) shares	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	May 31, 2018 USD ($) $ / shares
Debt Instrument [Line Items]
Convertible notes share settlement				$ 96,902	$ 799	$ 0
2025 Convertible Notes | Senior Notes
Debt Instrument [Line Items]
Stated interest rate		2.375%					2.375%
Convertible notes share settlement			$ 97,000
Debt conversion, further issued (in shares) | shares			6.1
Repayments of debt	$ 6,400
Principal amount							$ 172,500
Conversion rate per $1,000 principal amount (in shares)		0.0628931
Conversion price, per share (in dollars per share) | $ / shares							$ 15.90