CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings
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	59,038			59,038
Stock-based compensation expense	3,258		3,258
Shares issued under employee stock plans, net (in shares)		675
Forfeiture and other settlements of restricted stock (in shares)		(3)
Common stock redeemed for tax liability (in shares)		(205)
Common stock redeemed for tax liability	(2,597)		(2,597)
Ending balance (in shares) at Mar. 31, 2023		31,347
Ending balance at Mar. 31, 2023	998,985	$ 31	860,517	138,437
Beginning balance (in shares) at Dec. 31, 2022		31,347
Beginning balance at Dec. 31, 2022	962,600	$ 31	858,839	103,730
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income and comprehensive income	34,707			34,707
Stock-based compensation expense	1,678		1,678
Shares issued under employee stock plans, net (in shares)		3
Forfeiture and other settlements of restricted stock (in shares)		(3)
Ending balance (in shares) at Mar. 31, 2023		31,347
Ending balance at Mar. 31, 2023	998,985	$ 31	860,517	138,437
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	60,899			60,899
Stock-based compensation expense	3,062		3,062
Stock option exercises (in shares)		2
Stock option exercises	16		16
Shares issued under employee stock plans, net (in shares)		376
Shares issued under employee stock plans, net	1	$ 1
Forfeiture and other settlements of restricted stock (in shares)		(10)
Common stock redeemed for tax liability (in shares)		(172)
Common stock redeemed for tax liability	(5,220)		(5,220)
Ending balance (in shares) at Mar. 31, 2024		31,547
Ending balance at Mar. 31, 2024	1,161,577	$ 32	862,636	298,909
Beginning balance (in shares) at Dec. 31, 2023		31,533
Beginning balance at Dec. 31, 2023	1,121,011	$ 32	861,241	259,738
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income and comprehensive income	39,171			39,171
Stock-based compensation expense	1,389		1,389
Stock option exercises (in shares)		2
Stock option exercises	16		16
Shares issued under employee stock plans, net (in shares)		14
Forfeiture and other settlements of restricted stock (in shares)		(2)
Common stock redeemed for tax liability	(10)		(10)
Ending balance (in shares) at Mar. 31, 2024		31,547
Ending balance at Mar. 31, 2024	$ 1,161,577	$ 32	$ 862,636	$ 298,909