Net Income (Loss) Per Share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Numerator: Basic and Diluted
Net income (loss)	$ (1,162)	$ 11,719	$ (934)	$ 18,100
Dividends paid	(2,746)	(2,737)	(5,492)	(5,475)
Undistributed income (loss)	$ (3,908)	$ 8,982	$ (6,426)	$ 12,625
Percentage allocated to common shares	100.00%	99.10%	100.00%	99.10%
Undistributed income (loss) allocated to common shares	$ (3,870)	$ 8,901	$ (6,364)	$ 12,511
Dividends paid on common shares outstanding	2,719	2,712	5,439	5,425
Net income (loss) available to common shares	$ (1,151)	$ 11,613	$ (925)	$ 17,936
Denominator: Basic and Diluted
Weighted average common shares outstanding	12,360,369	12,333,550	12,352,926	12,329,716
Adjustment for dilutive potential common shares		11,866		12,395
Weighted average shares - Diluted	12,360,369	12,345,416	12,352,926	12,342,111
Basic net income (loss) per share (in dollars per share)	$ (0.09)	$ 0.94	$ (0.07)	$ 1.45
Diluted net income (loss) per share (in dollars per share)	$ (0.09)	$ 0.94	$ (0.07)	$ 1.45