Income Taxes - Aggregate Changes in Balance of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Balance at the beginning of the year	$ 76,590	$ 87,144
Beginning balance adjustment	4,977	(13,181)
Increases related to tax positions taken from prior periods		2,277
Decreases related to tax positions taken from prior periods	(1,476)
Increases related to tax positions taken during current period	5,382	2,088
Decreases for tax settlements and lapse in statutes	(301)	(1,738)
Balance at the end of the year	$ 85,172	$ 76,590