Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Statements of Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Condensed Statement of Income Captions [Line Items]
Comprehensive income (loss)	$ 14,807	$ 35,818	$ (12,825)	$ 52,525
Parent Company [Member]
Condensed Statement of Income Captions [Line Items]
Net income (loss) of subsidiaries	16,273	35,818	9,563	52,525
Comprehensive income (loss)	$ 14,807	$ 35,818	$ 12,825	$ 52,525