Stock-based compensation - Activity Under The Equity Incentive Plans (Details) shares in Thousands	12 Months Ended
	Sep. 30, 2024 $ / shares shares
Restricted Stock Unit
Number of Shares
Non vested shares beginning balance (in shares) | shares	1,620
Granted (in shares) | shares	1,523
Vested/Issued (in shares) | shares	(786)
Forfeited (in shares) | shares	(393)
Non vested shares ending balance (in shares) | shares	1,964
Weighted average grant date fair value per share
Weighted average grant date fair value, beginning balance (in dollars per share) | $ / shares	$ 40.73
Granted (in dollars per share) | $ / shares	28.01
Vested/ Issued (in dollars per share) | $ / shares	39.39
Forfeited (in dollars per share) | $ / shares	37.29
Weighted average grant date fair value, ending balance (in dollars per share) | $ / shares	$ 32.13
Performance Stock Unit
Number of Shares
Non vested shares beginning balance (in shares) | shares	932
Granted (in shares) | shares	617
Vested/Issued (in shares) | shares	(87)
Forfeited (in shares) | shares	(296)
Non vested shares ending balance (in shares) | shares	1,166
Weighted average grant date fair value per share
Weighted average grant date fair value, beginning balance (in dollars per share) | $ / shares	$ 36.82
Granted (in dollars per share) | $ / shares	18.71
Vested/ Issued (in dollars per share) | $ / shares	79.66
Forfeited (in dollars per share) | $ / shares	25.19
Weighted average grant date fair value, ending balance (in dollars per share) | $ / shares	$ 27.01