Income Taxes - Current and Deferred Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Deferred Income Tax Assets And Liabilities
Income (loss) before income taxes	$ (14,353)	$ (15,963)	$ 120,253	$ 154,041
Current income tax expense (benefit)	(7,058)	(3,968)	27,135	30,389
Deferred income tax expense	3,292	59	7,837	12,682
Total income tax expense (benefit)	$ (3,766)	$ (3,909)	$ 34,972	$ 43,071