CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings (Accumulated Deficit)
Beginning balance (in shares) at Sep. 30, 2021		31,294
Beginning balance at Sep. 30, 2021	$ 724,884	$ 31	$ 866,158	$ (141,305)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	133,881			133,881
Net comprehensive income	133,881			133,881
Stock-based compensation expense	6,515		6,515
Stock option exercises (in shares)		1
Stock option exercises	5		5
Shares issued under employee stock plans, net (in shares)		518
Forfeiture and other settlements of restricted stock (in shares)		(55)
Common stock redeemed for tax liability (in shares)		(308)
Common stock redeemed for tax liability	(6,631)		(6,631)
Share repurchases (in shares)		(175)
Share repurchases	(2,527)		(2,527)
Ending balance (in shares) at Jun. 30, 2022		31,275
Ending balance at Jun. 30, 2022	856,127	$ 31	863,520	(7,424)
Beginning balance (in shares) at Mar. 31, 2022		31,458
Beginning balance at Mar. 31, 2022	802,357	$ 31	864,074	(61,748)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	54,324			54,324
Net comprehensive income	54,324			54,324
Stock-based compensation expense	1,983		1,983
Stock option exercises	1		1
Shares issued under employee stock plans, net (in shares)		1
Forfeiture and other settlements of restricted stock (in shares)		(8)
Common stock redeemed for tax liability (in shares)		(1)
Common stock redeemed for tax liability	(11)		(11)
Share repurchases (in shares)		(175)
Share repurchases	(2,527)		(2,527)
Ending balance (in shares) at Jun. 30, 2022		31,275
Ending balance at Jun. 30, 2022	856,127	$ 31	863,520	(7,424)
Beginning balance (in shares) at Sep. 30, 2022		30,880
Beginning balance at Sep. 30, 2022	939,286	$ 31	859,856	79,399
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	102,855			102,855
Net comprehensive income	102,855			102,855
Stock-based compensation expense	5,247		5,247
Stock option exercises (in shares)		2
Stock option exercises	12		12
Shares issued under employee stock plans, net (in shares)		675
Forfeiture and other settlements of restricted stock (in shares)		(12)
Common stock redeemed for tax liability (in shares)		(206)
Common stock redeemed for tax liability	(2,615)		(2,615)
Ending balance (in shares) at Jun. 30, 2023		31,339
Ending balance at Jun. 30, 2023	1,044,785	$ 31	862,500	182,254
Beginning balance (in shares) at Mar. 31, 2023		31,347
Beginning balance at Mar. 31, 2023	998,985	$ 31	860,517	138,437
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,817			43,817
Net comprehensive income	43,817			43,817
Stock-based compensation expense	1,989		1,989
Stock option exercises (in shares)		2
Stock option exercises	12		12
Forfeiture and other settlements of restricted stock (in shares)		(9)
Common stock redeemed for tax liability (in shares)		(1)
Common stock redeemed for tax liability	(18)		(18)
Ending balance (in shares) at Jun. 30, 2023		31,339
Ending balance at Jun. 30, 2023	$ 1,044,785	$ 31	$ 862,500	$ 182,254