Earnings per Share - Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Numerator for diluted and basic earnings per share:
Net income	$ 97,643	$ 84,959
Denominator — share:
Basic weighted-average shares (in shares)	25,045	27,167
Effect of dilutive securities (in shares)	398	357
Diluted weighted-average shares (in shares)	25,443	27,524
Earnings per share:
Basic (in dollars per share)	$ 3.90	$ 3.13
Diluted (in dollars per share)	$ 3.84	$ 3.09