Stock Based Compensation (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Stock options, additional information
Proceeds from exercise of stock options			$ 807,990	$ 113,142
Stock options
Stock Based Compensation
Granted - options (in shares)	0	0	0	0
Stock options, shares
Outstanding at the beginning of the period (in shares)			1,501,500	1,588,750
Exercised (in shares)			(165,250)	(52,250)
Forfeited (in shares)			(21,750)
Outstanding at the end of the period (in shares)	1,314,500	1,536,500	1,314,500	1,536,500
Exercisable at the end of the period (in shares)	1,193,000	1,273,500	1,193,000	1,273,500
Stock options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)			$ 9.69	$ 9.39
Exercised (in dollars per share)			$ 4.89	$ 2.17
Forfeited (in dollars per share)			$ 11.64
Outstanding at the end of period (in dollars per share)	$ 10.26	$ 9.64	$ 10.26	$ 9.64
Exercisable at the end of the period (in shares)	$ 10.16	$ 9.29	$ 10.16	$ 9.29
Stock options, Weighted Average Remaining Contractual Life
Outstanding at the end of the period			5 years	5 years 6 months
Exercisable at the end of the period			4 years 8 months 12 days	5 years
Stock options, Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	5,752,000	2,191,000	5,752,000	2,191,000
Exercisable at the end of the period (in dollars)	5,340,000	2,191,000	5,340,000	2,191,000
Stock options, additional information
Compensation expense (in dollars)	76,000	186,000	208,000	474,000
Unrecognized compensation cost (in dollars)	246,000		246,000
Unamortized cost is expected to be recognized over a weighted-average period			1 year 3 months 18 days
Proceeds from exercise of stock options			808,000	113,000
Intrinsic value of shares exercised (in dollars)			$ 1,153,000	$ 220,000