Income Taxes - Current and Deferred Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Deferred Income Tax Assets And Liabilities
Income (loss) before income taxes	$ (33,196)	$ (14,353)	$ 72,100	$ 120,253
Current income tax expense (benefit)	(11,385)	(7,058)	30,710	27,135
Deferred income tax expense (benefit)	2,095	3,292	(10,284)	7,837
Total income tax expense (benefit)	$ (9,290)	$ (3,766)	$ 20,426	$ 34,972