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	79,557			79,557
Net comprehensive income	79,557			79,557
Stock-based compensation expense	4,532		4,532
Stock option exercises (in shares)		1
Stock option exercises	4		4
Shares issued under employee stock plans, net (in shares)		517
Forfeiture and other settlements of restricted stock (in shares)		(47)
Common stock redeemed for tax liability (in shares)		(307)
Common stock redeemed for tax liability	(6,620)		(6,620)
Ending balance (in shares) at Mar. 31, 2022		31,458
Ending balance at Mar. 31, 2022	802,357	$ 31	864,074	(61,748)
Beginning balance (in shares) at Dec. 31, 2021		31,460
Beginning balance at Dec. 31, 2021	755,259	$ 31	861,648	(106,420)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,672			44,672
Net comprehensive income	44,672			44,672
Stock-based compensation expense	2,424		2,424
Stock option exercises	$ 4		4
Shares issued under employee stock plans, net (in shares)	1
Forfeiture and other settlements of restricted stock (in shares)		(3)
Common stock redeemed for tax liability	$ (2)		(2)
Ending balance (in shares) at Mar. 31, 2022		31,458
Ending balance at Mar. 31, 2022	802,357	$ 31	864,074	(61,748)
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	59,038			59,038
Net 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	34,707			34,707
Net 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