CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings (Accumulated Deficit)
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 and comprehensive income	24,331			24,331
Stock-based compensation expense	1,580		1,580
Shares issued under employee stock plans, net (in shares)		672
Common stock redeemed for tax liability (in shares)		(205)
Common stock redeemed for tax liability	(2,597)		(2,597)
Ending balance (in shares) at Dec. 31, 2022		31,347
Ending balance at Dec. 31, 2022	962,600	$ 31	858,839	103,730
Beginning balance (in shares) at Sep. 30, 2023		31,351
Beginning 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	21,728			21,728
Stock-based compensation expense	1,673		1,673
Shares issued under employee stock plans, net (in shares)		362
Shares issued under employee stock plans, net	1	$ 1
Forfeiture and other settlements of restricted stock (in shares)		(8)
Common stock redeemed for tax liability (in shares)		(172)
Common stock redeemed for tax liability	(5,210)		(5,210)
Ending balance (in shares) at Dec. 31, 2023		31,533
Ending balance at Dec. 31, 2023	$ 1,121,011	$ 32	$ 861,241	$ 259,738