Stock-based Compensation - Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares
Shares
Beginning balance (in shares) | shares	1,892
Forfeited (in shares) | shares	(61)
Exercised (in shares) | shares	(238)
Ending balance (in shares) | shares	1,593	1,892
Number of options, Exercisable (in shares) | shares	1,562
Weighted average exercise price per share
Beginning balance (in usd per share) | $ / shares	$ 29.60
Forfeited (in usd per share) | $ / shares	67.88
Exercised (in dollars per share) | $ / shares	15.64
Ending balance (in usd per share) | $ / shares	30.23	$ 29.60
Vested and exercisable (in usd per share) | $ / shares	$ 30.14
Weighted average remaining contractual term (years)
Outstanding	4 years 2 months 8 days	4 years 6 months 25 days
Weighted average remaining contractual term (years), Exercisable	4 years 1 month 17 days
Aggregate Intrinsic Value
Aggregate intrinsic value, outstanding beginning balance | $	$ 37,840
Exercised | $	7,154
Aggregate intrinsic value, outstanding ending balance | $	22,643	$ 37,840
Aggregate intrinsic value, Vested and exercisable | $	$ 22,404