Forward Currency Contracts - Summary of Average Outstanding Daily Volume for Forward Currency Contract (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Foreign exchange
Open Forward Foreign Currency Contract [Line Items]
Average U.S. Dollar notional outstanding	$ 221,448	$ 254,118	$ 94,304