Summary of Significant Accounting Policies - Goodwill and Other Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Accounting Policies [Abstract]
Loss on impairment	$ 57,710	$ 0
Intangible asset estimated useful lives (in years)	10 years
Impairment of intangible assets, finite-lived	$ 89,700	$ 0