Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Numerator
Net income	$ 144,079	$ 88,976	$ 401,482	$ 242,814
Denominator
Weighted average shares outstanding — basic (shares)	58,584	59,977	58,832	60,133
Dilutive effect of common shares from stock options and restricted stock units	563	337	629	330
Weighted average shares outstanding — diluted (shares)	59,147	60,314	59,461	60,463
Basic net income per share (dollars per share)	$ 2.46	$ 1.48	$ 6.82	$ 4.04
Diluted net income per share (dollars per share)	$ 2.44	$ 1.48	$ 6.75	$ 4.02