CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Sep. 30, 2013		25,246
Beginning balance at Sep. 30, 2013	$ 240,550	$ 25	$ 846,165	$ (605,640)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,383			34,383
Change in unrealized loss related to available-for-sale securities	(1,276)				(1,276)
Total comprehensive income	33,107
Conversion of TEU (debt to stock conversion) (in shares)		1,368
Conversion of TEU (debt to stock conversion)	2,484	$ 2	2,482
Amortization of nonvested stock awards	2,587		2,587
Exercises of stock options (in shares)		3
Exercises of stock options	39		39
Tax excess (deficiency) from stock transactions	698		698
Shares issued under employee stock plans, net (in shares)		596
Shares issued under employee stock plans, net	103		103
Forfeiture of restricted stock (in shares)		(16)
Forfeiture of restricted stock	0
Common stock redeemed (in shares)		(24)
Common stock redeemed	(450)		(450)
Ending balance (in shares) at Sep. 30, 2014		27,173
Ending balance at Sep. 30, 2014	279,118	$ 27	851,624	(571,257)	(1,276)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	344,094			344,094
Change in unrealized loss related to available-for-sale securities	1,276				1,276
Total comprehensive income	345,370
Conversion of TEU (debt to stock conversion) (in shares)		5,222
Conversion of TEU (debt to stock conversion)	1	$ 5	(4)
Amortization of nonvested stock awards	6,135		6,135
Exercises of stock options (in shares)		1
Exercises of stock options	14		14
Tax excess (deficiency) from stock transactions	(22)		(22)
Shares issued under employee stock plans, net (in shares)		410
Shares issued under employee stock plans, net	0	$ 0	0
Forfeiture of restricted stock (in shares)		(135)
Forfeiture of restricted stock	0
Common stock redeemed (in shares)		(10)
Common stock redeemed	(192)		(192)
Other activity	(1)	$ 1	(2)
Ending balance (in shares) at Sep. 30, 2015		32,661
Ending balance at Sep. 30, 2015	630,423	$ 33	857,553	(227,163)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,693			4,693
Change in unrealized loss related to available-for-sale securities	0
Total comprehensive income	4,693
Amortization of nonvested stock awards	7,959		7,959
Shares issued under employee stock plans, net (in shares)		491
Shares issued under employee stock plans, net	0
Forfeiture of restricted stock (in shares)		(64)
Forfeiture of restricted stock	0
Common stock redeemed (in shares)		(17)
Common stock redeemed	(222)		(222)
Ending balance (in shares) at Sep. 30, 2016		33,071
Ending balance at Sep. 30, 2016	$ 642,853	$ 33	$ 865,290	$ (222,470)	$ 0