Debt Financing (Details) (USD $)	Jun. 30, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	$ 124,074,368		$ 124,648,502
Debt Financing, Current Maturities	10,340,000
Debt Financing, Maturities, Repayment of Principal in Year Two	1,009,000
Debt Financing, Maturities, Repayments of Principal in Year Three	1,083,000
Debt Financing, Maturities, Repayments of Principal in Year Four	1,139,000
Debt Financing, Maturities, Repayments of Principal in Year Five	1,192,000
Debt Financing, Maturities, Repayments of Principal after Year Five	89,565,000
Debt financing	104,328,000		112,673,000
Consolidated VIEs [Member]
Debt Instrument [Line Items]
Debt financing	0		0
Ashley Square [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	5,284,000		5,308,000
Bella Vista [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	6,600,000		6,650,000
Bent Tree [Member] | Consolidated VIEs [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	7,650,000		7,686,000
Bridle Ridge [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	7,790,000		7,815,000
Brookstone [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	9,454,309		9,490,809
Cross Creek [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	8,602,059		8,634,693
Fairmont Oaks [Member] | Consolidated VIEs [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	7,481,000		7,520,000
Lake Forest [Member] | Consolidated VIEs [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	9,153,000		9,201,000
Runnymede [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	10,645,000		10,685,000
Southpark [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	14,000,000		14,000,000
Woodlynn Village [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	4,476,000		4,492,000
Ohio Properties [Member] | MF Properties [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	14,624,000	[1]	14,666,000	[1]
Lost Creek [Member] | Tax-exempt bond investments [Member]
Debt Instrument [Line Items]
Available for Sale Securities at Par Value	$ 18,315,000		$ 18,500,000

[1] Collateralized by Crescent Village, Postwoods and Willow Bend (Note 2)