Stock-based compensation expense - Activity Under The Equity Incentive Plans (Details) shares in Thousands	3 Months Ended
	Dec. 31, 2023 $ / shares shares
Restricted Stock Unit
Number of Shares
Beginning balance (in shares) | shares	1,620
Granted (in shares) | shares	1,035
Vested/Issued (in shares) | shares	(152)
Forfeited (in shares) | shares	(84)
Ending balance (in shares) | shares	2,419
Weighted average grant date fair value per share
Beginning balance (in usd per share) | $ / shares	$ 40.73
Granted (in usd per share) | $ / shares	22.14
Vested (in usd per share) | $ / shares	43.58
Forfeited (in usd per share) | $ / shares	50.29
Ending balance (in usd per share) | $ / shares	$ 32.29
Performance Stock Unit
Number of Shares
Beginning balance (in shares) | shares	932
Granted (in shares) | shares	570
Vested/Issued (in shares) | shares	(82)
Forfeited (in shares) | shares	(15)
Ending balance (in shares) | shares	1,405
Weighted average grant date fair value per share
Beginning balance (in usd per share) | $ / shares	$ 36.82
Granted (in usd per share) | $ / shares	17.31
Vested (in usd per share) | $ / shares	80.27
Forfeited (in usd per share) | $ / shares	48.37
Ending balance (in usd per share) | $ / shares	$ 26.23