Income Taxes - Current and Deferred Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Deferred Income Tax Assets And Liabilities
Income (loss) before income taxes	$ (15,201)	$ (33,196)	$ 99,196	$ 72,100
Current income tax expense (benefit)	(4,418)	(11,385)	31,382	30,710
Deferred income tax expense (benefit)	261	2,095	(2,495)	(10,284)
Total income tax expense (benefit)	$ (4,157)	$ (9,290)	$ 28,887	$ 20,426