Consolidated Statement of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Sep. 30, 2010	$ 136,586	$ 122	$ 46,998	$ 89,622	$ (156)
Beginning Balance, Shares at Sep. 30, 2010		12,234,716
Net income	29,711			29,711
Other comprehensive income (loss)	326				326
Excess tax benefit from share-based compensation	6,896		6,896
Issuance of common stock pursuant to exercise of options, net of tax	2,758	6	2,752
Issuance of common stock pursuant to exercise of options, Shares	467,800	467,800
Stock-based compensation	736		736
Ending Balance at Sep. 30, 2011	177,013	128	57,382	119,333	170
Ending Balance, Shares at Sep. 30, 2011		12,702,516
Net income	35,118			35,118
Other comprehensive income (loss)	(395)				(395)
Excess tax benefit from share-based compensation	1,131		1,131
Issuance of common stock pursuant to exercise of options, net of tax	1,358		1,358
Issuance of common stock pursuant to exercise of options, Shares	99,644	99,644
Stock-based compensation	762		762
Ending Balance at Sep. 30, 2012	214,987	128	60,633	154,451	(225)
Ending Balance, Shares at Sep. 30, 2012		12,802,160
Net income	69,557			69,557
Other comprehensive income (loss)	(839)				(839)
Excess tax benefit from share-based compensation	3,390		3,390
Issuance of common stock pursuant to exercise of options, net of tax	1,419	1	1,418
Issuance of common stock pursuant to exercise of options, Shares	139,906	139,906
Stock-based compensation	544		544
Ending Balance at Sep. 30, 2013	$ 289,058	$ 129	$ 65,985	$ 224,008	$ (1,064)
Ending Balance, Shares at Sep. 30, 2013		12,942,066