Income per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income available to common shareholders (in thousands)	$ 9,343	$ 6,818	$ 16,456	$ 12,600
Weighted average common shares outstanding (shares)	28,666,249	27,250,810	28,567,974	27,453,705
Effect of dilutive securities
Options (shares)	1,681,902	1,404,417	1,684,415	1,123,574
Weighted average common and potential shares outstanding (shares)	30,348,151	28,655,227	30,252,389	28,577,279
Basic income per share (usd per share)	$ 0.33	$ 0.25	$ 0.58	$ 0.46
Diluted income per share (usd per share)	$ 0.31	$ 0.24	$ 0.54	$ 0.44
Exercise price, lower range (usd per share)	$ 13.00	$ 6.73	$ 11.33	$ 5.75
Exercise price, upper limit (usd per share)	$ 19.67	$ 18.71	$ 19.67	$ 18.71
Stock Options
Effect of dilutive securities
Options to purchase shares of common stock (shares)	42,957	1,100,000	141,290	1,100,000