Income Taxes - Current and Deferred Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Deferred Income Tax Assets And Liabilities
Income before income taxes	$ 86,294	$ 114,279	$ 105,296	$ 134,606
Current income tax expense	35,408	27,671	42,095	34,193
Deferred income tax benefit	(11,155)	5,229	(12,379)	4,545
Total income tax expense	$ 24,253	$ 32,900	$ 29,716	$ 38,738