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, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ (1,833)	$ 3,752	$ 10,816	$ 24,176	$ 13,684	$ 16,991	$ 16,869	$ 22,013	$ 36,911	$ 69,557	$ 35,118
Less: Income allocable to unvested restricted stock									(444)
Income available to common shareholders									36,467	69,557	35,118
Reallocation of participating earnings									2
Income attributable to common shareholders for diluted earnings per share									$ 36,469	$ 69,557	$ 35,118
Weighted average number of common share equivalents:
Common shares used in basic earnings per share									12,950,958	12,886,372	12,735,520
Common share equivalents outstanding related to stock options									46,051	52,289	100,719
Total weighted average common shares and common share equivalents used in diluted earnings per share									12,997,009	12,938,661	12,836,239
Basic	$ (0.14)	$ 0.29	$ 0.83	$ 1.86	$ 1.06	$ 1.32	$ 1.31	$ 1.72	$ 2.82	$ 5.40	$ 2.76
Diluted	$ (0.14)	$ 0.29	$ 0.82	$ 1.85	$ 1.05	$ 1.31	$ 1.30	$ 1.70	$ 2.81	$ 5.38	$ 2.74