Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Retained Earnings [Member]
Beginning balance at Sep. 30, 2014	$ 37,414	$ 10,852	$ 26,562
Beginning balance, Shares at Sep. 30, 2014		9,028,914
Net income	11,389		11,389
Dividends paid	(1,383)		(1,383)
Employee and director restricted stock vested	0	$ 0	0
Employee and director restricted stock vested, Shares		51,113
Repurchase of common stock pursuant to self- tender offer, including costs of $55,655	(25,056)		(25,056)
Repurchase of common stock pursuant to self- tender offer, including costs of $55,655, Shares		(1,500,000)
Repurchase of vested employee restricted stock for tax withholding	(139)	$ (71)	(68)
Repurchase of vested employee restricted stock for tax withholding, Shares		(10,280)
Shares issued for auto-investments pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan, Shares		18
Shares issued for dividend reinvestment pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan		$ 3	(3)
Shares issued for dividend reinvestment pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan, Shares		177
Stock-based compensation	692	$ 692
Tax effect of restricted stock unit vesting	178	178
Ending balance at Sep. 30, 2015	23,095	$ 11,654	11,441
Ending balance, shares at Sep. 30, 2015		7,569,942
Net income	14,367		14,367
Dividends paid	(1,500)		(1,500)
Employee and director restricted stock vested	0	$ 0	0
Employee and director restricted stock vested, Shares		119,250
Repurchase of vested employee restricted stock for tax withholding	(518)	$ (282)	(236)
Repurchase of vested employee restricted stock for tax withholding, Shares		(28,872)
Shares issued for auto-investments pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan	15	$ 15
Shares issued for auto-investments pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan, Shares		735
Shares issued for dividend reinvestment pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan		$ 20	(20)
Shares issued for dividend reinvestment pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan, Shares		914
Stock-based compensation	1,416	$ 1,416
Tax effect of restricted stock unit vesting	456	456
Ending balance at Sep. 30, 2016	37,331	$ 13,279	24,052
Ending balance, shares at Sep. 30, 2016		7,661,969
Net income	14,942		14,942
Dividends paid	(2,243)		(2,243)
Employee and director restricted stock vested	0	$ 0	0
Employee and director restricted stock vested, Shares		152,322
Repurchase of vested employee restricted stock for tax withholding	(653)	$ (489)	(164)
Repurchase of vested employee restricted stock for tax withholding, Shares		(39,820)
Shares issued for auto-investments pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan	3	$ 3
Shares issued for auto-investments pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan, Shares		183
Shares issued for dividend reinvestment pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan	33	$ 33
Shares issued for dividend reinvestment pursuant to the 2015 Dividend Reinvestment and Stock Purchase Plan, Shares		1,965
Stock-based compensation	2,118	$ 2,118
Adjustment for fractional shares paid in cash in connection with stock split	(1)	$ (1)
Adjustment for fractional shares paid in cash in connection with stock split, Shares		(56)
Ending balance at Sep. 30, 2017	$ 51,530	$ 14,943	$ 36,587
Ending balance, shares at Sep. 30, 2017		7,776,563