2023 Restructuring and other costs - Accrual Activity and Payments Relating to Cash-Based Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs	$ 0	$ 9,384	$ 0
2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs		9,384
Payments		(8,867)
Restructuring reserve		517
Severance and related benefit costs | 2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs		8,467
Payments		(7,950)
Restructuring reserve		517
Other associated costs | 2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and other costs		917
Payments		(917)
Restructuring reserve		$ 0