Net Income (Loss) Per Share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Numerator: Basic and Diluted
Net income (loss) - Basic	$ 4,068	$ 1,509	$ 7,336	$ (94)
Net income (loss) - Diluted	4,068	1,509	7,336	(94)
Dividends	(2,781)	(2,758)	(5,618)	(5,517)
Undistributed income (loss) - Basic	1,287	(1,249)	1,718	(5,611)
Undistributed income (loss) - Diluted	$ 1,287	$ (1,249)	$ 1,718	$ (5,611)
Percentage allocated to common shares	99.30%	100.00%	99.30%	100.00%
Undistributed income (loss) allocated to common shares - Basic	$ 1,279	$ (1,249)	$ 1,707	$ (5,611)
Undistributed income (loss) allocated to common shares - Diluted	1,279	(1,249)	1,707	(5,611)
Dividends paid on common shares outstanding	2,763	2,738	5,581	5,475
Net income (loss) available to common shares - Basic	4,042	1,489	7,288	(136)
Net income (loss) available to common shares - Diluted	$ 4,042	$ 1,489	$ 7,288	$ (136)
Denominator: Basic and Diluted
Weighted average common shares outstanding - Basic	12,473,881	12,448,792	12,466,867	12,439,689
Adjustment for dilutive potential common shares	30,182	151,500	30,082
Weighted average shares outstanding - Diluted	12,504,063	12,600,292	12,496,949	12,439,689
Basic net income (loss) per share (in dollars per share)	$ 0.32	$ 0.12	$ 0.58	$ (0.01)
Diluted net income (loss) per share (in dollars per share)	$ 0.32	$ 0.12	$ 0.58	$ (0.01)