Calculation of Weighted Average Common Shares and Common Equivalent Shares Outstanding (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income	$ 3,752	$ 16,991	$ 38,744	$ 55,873
Less: Income allocable to unvested restricted stock	(43)		(439)
Income available to common shareholders	3,709	16,991	38,305	55,873
Reallocation of participating earnings			1
Diluted income attributable to common shareholders	$ 3,709	$ 16,991	$ 38,306	$ 55,873
Weighted average number of common share equivalents:
Common shares used in basic earnings per share	12,951,845	12,911,316	12,949,807	12,873,677
Common share equivalents outstanding related to stock options	47,962	71,006	50,296	69,428
Total weighted average common shares and common share equivalents used in diluted earnings per share	12,999,807	12,982,322	13,000,103	12,943,105
Basic earnings per common share	$ 0.29	$ 1.32	$ 2.96	$ 4.34
Diluted earnings per common share	$ 0.29	$ 1.31	$ 2.95	$ 4.32