Summary of Significant Accounting Policies - Foreign Currency Translation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Gain (Loss), Foreign Currency Transaction, before Tax [Abstract]
Foreign currency transaction and remeasurement gains (losses)	$ 4,200	$ 1,700	$ 1,800
Foreign currency translation reclassification adjustments included in income from discontinued operations		$ (16,567)