Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Data (Unaudited)
Interest Income	$ 14,666,000	$ 14,768,000	$ 14,930,000	$ 15,553,000	$ 16,406,000	$ 17,044,000	$ 18,460,000	$ 19,159,000	$ 20,524,000	$ 21,734,000	$ 22,696,000	$ 23,189,000	$ 59,917,000	$ 71,069,000	$ 88,143,000
Net Interest Income	11,737,000	11,584,000	11,511,000	11,869,000	12,335,000	12,295,000	13,158,000	13,449,000	13,687,000	13,935,000	14,421,000	14,306,000	46,701,000	51,237,000	56,349,000
Net Income (Loss) Attributable to Common Shares	$ 3,049,000	$ 2,616,000	$ 3,288,000	$ 2,552,000	$ 29,991,000	$ 2,682,000	$ 2,381,000	$ 1,088,000	$ (5,282,000)	$ (5,682,000)	$ (684,000)	$ (2,963,000)	$ 11,505,000	$ 36,142,000	$ (14,611,000)
Basic	$ 0.35	$ 0.30	$ 0.38	$ 0.30	$ 3.49	$ 0.31	$ 0.28	$ 0.13	$ (0.62)	$ (0.67)	$ (0.08)	$ (0.35)	$ 1.33	$ 4.20	$ (1.72)
Diluted	$ 0.35	$ 0.30	$ 0.36	$ 0.28	$ 3.37	$ 0.30	$ 0.27	$ 0.12	$ (0.62)	$ (0.67)	$ (0.08)	$ (0.35)	$ 1.30	$ 4.07	$ (1.72)