Variable Interest Entities Property Asset Carrying Value and Maximum Exposure (Details) (USD $)	Mar. 31, 2015
Mortgage revenue bonds [Member]
Maximum Exposure to Loss	$ 67,088,064
Carrying Value	72,991,378
Property Loan [Member]
Maximum Exposure to Loss	11,221,635
Carrying Value	5,068,115
Ashley Square [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	5,144,000
Carrying Value	5,642,269
Ashley Square [Member] | Property Loan [Member]
Maximum Exposure to Loss	7,635,520
Carrying Value	1,482,000
Bruton Apts [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	18,145,000
Carrying Value	19,443,819
Bruton Apts [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	0
Cross Creek [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	6,082,064
Carrying Value	8,547,448
Cross Creek [Member] | Property Loan [Member]
Maximum Exposure to Loss	3,586,115
Carrying Value	3,586,115
Glenview Apts [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	6,723,000
Carrying Value	6,855,286
Glenview Apts [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	0
Harden Ranch [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	9,300,000
Carrying Value	9,920,953
Harden Ranch [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	0
Montclair Apts [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	3,458,000
Carrying Value	3,606,478
Montclair Apts [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	0
Santa Fe Apts [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	4,736,000
Carrying Value	4,856,631
Santa Fe Apts [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	0
Tyler Park Apartments [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	8,100,000
Carrying Value	8,474,338
Tyler Park Apartments [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	0
Westside Village Market [Member] | Mortgage revenue bonds [Member]
Maximum Exposure to Loss	5,400,000
Carrying Value	5,644,156
Westside Village Market [Member] | Property Loan [Member]
Maximum Exposure to Loss	0
Carrying Value	$ 0