CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	(Accumulated Deficit) Retained Earnings
Beginning balance (in shares) at Sep. 30, 2021		31,294,000
Beginning balance at Sep. 30, 2021	$ 724,884	$ 31	$ 866,158	$ (141,305)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income and comprehensive income	220,704			220,704
Stock-based compensation expense	8,478		8,478
Stock option exercises (in shares)		1,000
Stock option exercises	5		5
Shares issued under employee stock plans, net (in shares)		518,000
Forfeiture and other settlements of restricted stock (in shares)		(55,000)
Forfeiture and other settlements of restricted stock	0		0
Common stock redeemed for tax liability (in shares)		(308,000)
Common stock redeemed for tax liability	$ (6,631)		(6,631)
Share repurchases (in shares)	(570,000)	(570,000)
Share repurchases	$ (8,154)		(8,154)
Ending balance (in shares) at Sep. 30, 2022		30,880,000
Ending balance at Sep. 30, 2022	939,286	$ 31	859,856	79,399
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income and comprehensive income	158,611			158,611
Stock-based compensation expense	7,275		7,275
Stock option exercises (in shares)		14,000
Stock option exercises	262		262
Shares issued under employee stock plans, net (in shares)		675,000
Forfeiture and other settlements of restricted stock (in shares)		(12,000)
Forfeiture and other settlements of restricted stock	0		0
Common stock redeemed for tax liability (in shares)		(206,000)
Common stock redeemed for tax liability	$ (2,615)		(2,615)
Share repurchases (in shares)	0
Ending balance (in shares) at Sep. 30, 2023		31,351,000
Ending balance at Sep. 30, 2023	$ 1,102,819	$ 31	864,778	238,010
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income and comprehensive income	140,175			140,175
Stock-based compensation expense	7,391		7,391
Stock option exercises (in shares)		3,000
Stock option exercises	20		20
Shares issued under employee stock plans, net (in shares)		387,000
Shares issued under employee stock plans, net	1	$ 1
Forfeiture and other settlements of restricted stock (in shares)		(61,000)
Forfeiture and other settlements of restricted stock	0		0
Common stock redeemed for tax liability (in shares)		(177,000)
Common stock redeemed for tax liability	$ (5,366)		(5,366)
Share repurchases (in shares)	(455,000)	(455,000)
Share repurchases	$ (12,929)	$ (1)	(12,928)
Ending balance (in shares) at Sep. 30, 2024		31,048,000
Ending balance at Sep. 30, 2024	$ 1,232,111	$ 31	$ 853,895	$ 378,185