CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid in Capital	Accumulated Deficit
Beginning balance (in shares) at Sep. 30, 2016		33,071
Beginning balance at Sep. 30, 2016	$ 642,853	$ 33	$ 865,290	$ (222,470)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income and comprehensive (loss) income	31,813			31,813
Amortization of nonvested stock awards	8,164		8,164
Exercises of stock options (in shares)		2
Exercises of stock options	24		24
Shares issued under employee stock plans, net (in shares)		536
Shares issued under employee stock plans, net	1	$ 1	0
Forfeiture of restricted stock (in shares)		(61)
Forfeiture of restricted stock	0
Common stock redeemed for tax liability (in shares)		(32)
Common stock redeemed for tax liability	(415)		(415)
Ending balance (in shares) at Sep. 30, 2017		33,516
Ending balance at Sep. 30, 2017	682,440	$ 34	873,063	(190,657)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income and comprehensive (loss) income	(45,375)
Amortization of nonvested stock awards	10,258		10,258
Exercises of stock options (in shares)		8
Exercises of stock options	64		64
Shares issued under employee stock plans, net (in shares)		443
Shares issued under employee stock plans, net	0	$ 0
Forfeiture of restricted stock (in shares)		(216)
Forfeiture of restricted stock	0
Common stock redeemed for tax liability (in shares)		(229)
Common stock redeemed for tax liability	(3,378)		(3,378)
Other activity	18		18
Ending balance (in shares) at Sep. 30, 2018		33,522
Ending balance at Sep. 30, 2018	644,027	$ 34	880,025	(236,032)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income and comprehensive (loss) income	(79,520)
Amortization of nonvested stock awards	10,526		10,526
Exercises of stock options (in shares)		32
Exercises of stock options	314		314
Shares issued under employee stock plans, net (in shares)		917
Forfeiture of restricted stock (in shares)		(68)
Forfeiture of restricted stock	0
Common stock redeemed for tax liability (in shares)		(185)
Common stock redeemed for tax liability	(1,969)		(1,969)
Share repurchases (in shares)		(3,285)
Share repurchases	(34,624)	$ (3)	(34,621)
Ending balance (in shares) at Sep. 30, 2019		30,933
Ending balance at Sep. 30, 2019	$ 538,754	$ 31	$ 854,275	$ (315,552)