Calculation of Weighted Average Common Shares and Common Equivalent Shares Outstanding (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
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income	$ 13,684	$ 16,991	$ 16,869	$ 22,013	$ 4,266	$ 10,736	$ 11,431	$ 8,685	$ 69,557	$ 35,118	$ 29,711
Weighted average common shares and common share equivalents:
Common shares									12,886,372	12,735,520	12,441,313
Common share equivalents									52,289	100,719	131,334
Total weighted average common shares and common share equivalents									12,938,661	12,836,239	12,572,647
Basic	$ 1.06	$ 1.32	$ 1.31	$ 1.72	$ 0.33	$ 0.84	$ 0.90	$ 0.68	$ 5.40	$ 2.76	$ 2.39
Diluted	$ 1.05	$ 1.31	$ 1.30	$ 1.70	$ 0.33	$ 0.83	$ 0.89	$ 0.68	$ 5.38	$ 2.74	$ 2.36