Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Statements of Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Condensed Statement of Income Captions [Line Items]
Comprehensive income (loss)	$ 75,225	$ 93,150	$ (122,233)
Parent Company [Member]
Condensed Statement of Income Captions [Line Items]
Net income (loss) of subsidiaries	75,225	93,150	(122,233)
Comprehensive income (loss)	$ 75,225	$ 93,150	$ (122,233)