Share-Based Compensation: (Details)		3 Months Ended	12 Months Ended
	Jan. 25, 2013 $ / shares	Mar. 31, 2013 USD ($)	Sep. 30, 2015 USD ($) item $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Sep. 30, 2013 USD ($) $ / shares shares
Share-based compensation
Share-based compensation expense | $			$ 447,000	$ 810,000	$ 912,000
Income tax effect recognized as a charge to additional paid-in capital related to share-based compensation | $			$ (35,000)	$ (253,000)	(33,000)
Number of share-based compensation plans maintained by the company | item			3
Options
Outstanding at the beginning of the period (in shares)			687,168
Outstanding at the end of the period (in shares)			645,168	687,168
Options
Share-based compensation
Reduction in applicable option exercise price of each outstanding option (in dollars per share) | $ / shares	$ 1.50
1998 Plan
Share-based compensation
Share-based compensation expense | $			$ 0	$ 0	$ 34,000
Number of shares of common stock reserved for awards			3,389,000
1998 Plan | Options
Share-based compensation
Unrecognized compensation cost, related to non-vested stock options | $			$ 0
Options
Outstanding at the beginning of the period (in shares)			62,000	144,500	376,200
Granted (in shares)			0	0	0
Exercised (in shares)				(12,000)	(226,800)
Cancelled (in shares)			(9,000)	(70,500)	(4,900)
Outstanding at the end of the period (in shares)			53,000	62,000	144,500
Vested and expected to vest (in shares)			53,000
Options exercisable at the end of the period (in shares)			53,000
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares			$ 9.91	$ 12.79	$ 8.62
Exercised (in dollars per share) | $ / shares				7.40
Cancelled (in dollars per share) | $ / shares			16.25	16.25	11.42
Outstanding at the end of the period (in dollars per share) | $ / shares			8.83	$ 9.91	$ 12.79
Vested and expected to vest (in dollars per share) | $ / shares			8.83
Options exercisable at the end of the period (in dollars per share) | $ / shares			8.83
Aggregate Intrinsic Value
Exercised (in dollars) | $				$ 8,604	$ 174,112
Weighted-average grant date fair value (in dollars per share) | $ / shares			0.00	$ 0.00	$ 4.63
Intrinsic value of options granted (in dollars per share) | $ / shares			$ 0	$ 0
2009 Plan
Share-based compensation
Share-based compensation expense | $			$ 316,000	$ 660,000	$ 678,000
Number of shares of common stock reserved for awards			1,200,000
Number of shares of common stock available for awards under the plan			347,755
2009 Plan | Options
Share-based compensation
Share-based compensation expense | $		$ 22,000
Unrecognized compensation cost, related to non-vested stock options | $		$ 59,000	$ 68,000
Options
Outstanding at the beginning of the period (in shares)			625,168	680,334	460,000
Granted (in shares)					250,000
Exercised (in shares)			(20,000)	(44,666)	(27,999)
Cancelled (in shares)			(13,000)	(10,500)	(1,667)
Outstanding at the end of the period (in shares)			592,168	625,168	680,334
Vested and expected to vest (in shares)			592,168
Options exercisable at the end of the period (in shares)			508,834
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares			$ 3.28	$ 3.32	$ 4.45
Granted (in dollars per share) | $ / shares					4.06
Exercised (in dollars per share) | $ / shares			1.95	3.78	3.78
Cancelled (in dollars per share) | $ / shares			2.37	3.78	3.78
Outstanding at the end of the period (in dollars per share) | $ / shares			3.35	$ 3.28	$ 3.32
Vested and expected to vest (in dollars per share) | $ / shares			3.35
Options exercisable at the end of the period (in dollars per share) | $ / shares			$ 3.23
Aggregate Intrinsic Value
Exercised (in dollars) | $			$ 15,200	$ 178,823	$ 118,802
Outstanding at the end of the period (in dollars) | $				$ 3,153,696
2009 Plan | Performance-based Award | Employee
Share-based compensation
Maximum award (in shares)			300,000