Income per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net Income available to common shareholders (in thousands)	$ 10,029	$ 8,449	$ 9,343	$ 7,113	$ 8,325	$ 7,249	$ 6,818	$ 5,782	$ 34,934	$ 28,174	$ 5,677
Weighted average common shares outstanding (shares)									28,929,177	27,806,840	28,105,824
Effect of dilutive securities
Options (shares)									1,747,510	1,454,508	580,431
Weighted average common and potential shares outstanding (shares)	30,936,000	30,710,000	30,348,000	30,017,000	29,828,000	29,275,000	28,655,000	28,109,000	30,676,687	29,261,348	28,686,255
Basic income per share (usd per share)									$ 1.21	$ 1.01	$ 0.20
Diluted income per share (usd per share)	$ 0.32	$ 0.28	$ 0.31	$ 0.24	$ 0.28	$ 0.25	$ 0.24	$ 0.21	$ 1.14	$ 0.96	$ 0.20
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (shares)									10,733	531,677	3,600,000