Income Taxes - Summary of Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Domestic	$ 418,265	$ 43,504	$ (49,193)
Foreign	501,912	425,458	381,759
Income before income taxes	$ 920,177	$ 468,962	$ 332,566