Investments in Tax-Exempt Bonds Investments of Tax-Exempt Bonds Autumn Pines (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Feb. 28, 2013
Payments to Acquire Available-for-sale Securities	$ 28,561,857		$ 20,917,500		$ 28,195,363
Available-for-sale Securities, at Par Value	146,806,203		145,907,502
Debt Instrument, Interest Rate, Stated Percentage						9.00%
Autumn Pines [Member]
Number of Units in Real Estate Property					250
Payments to Acquire Available-for-sale Securities					12,300,000
Available-for-sale Securities, at Par Value	13,220,000	[1]	13,325,000	[1]
Available-for-Sale Securities, Asset Ownership	100.00%
Available-for-sale Securities, original amount	$ 13,400,000
Debt Instrument, Interest Rate, Stated Percentage	5.80%	[1]	5.80%	[1]
Debt Instrument, Interest Rate, Effective Percentage					7.00%
Available-for-sale Security, Maturity Date at a point in time	Oct. 01, 2046	[1]	Oct. 01, 2046	[1]

[1] Bond held by Duetsche Bank in a secured financing transaction, Note 11