Subsequent Events Narrative Tagging (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($) Unit	Sep. 30, 2015 USD ($) Unit	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($) Unit	Jul. 01, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($) Unit
Subsequent Event [Line Items]
Property loans receivable	$ 24,995,110	$ 24,995,110					$ 22,191,515
Available for Sale Securities at Par Value	118,010,775	118,010,775					118,342,000
Assets	838,400,518	838,400,518					744,239,217
Debt financing	447,606,493	447,606,493					345,359,000
Long-term Purchase Commitment, Amount		42,665,912	$ 0
Mortgage revenue bonds held in trust, at fair value	499,197,562	499,197,562					$ 378,423,092
Payments to Acquire Available-for-sale Securities		137,805,000	$ 107,770,827
TEBS III Facility [Member] [Member]
Subsequent Event [Line Items]
Available for Sale Securities at Par Value	105,400,000	105,400,000
Debt financing	84,300,000	84,300,000
Debt Financing, Net	82,200,000
Payments to Acquire Available-for-sale Securities	37,500,000
Restricted Cash and Cash Equivalents	4,800,000	4,800,000
Derivative Asset, Notional Amount	$ 21,100,000	$ 21,100,000
Derivative, Fixed Interest Rate	3.00%	3.00%
Debt Instrument, Basis Spread on Variable Rate	0.03%
Short-term Debt, Percentage Bearing Fixed Interest Rate	1.30%	1.30%
Derivative, Variable Interest Rate	0.10%	0.10%
Cost of Issuance Rate	0.50%
Debt Instrument, Total Rate of Borrowing	2.00%	2.00%
Vantage at Brooks and Vantage at New Braunfels [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Property loans receivable				$ 17,000,000
Vantage at Brooks [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property | Unit				288
Vantage at New Braunfels [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property | Unit				288
Glynn Place [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property | Unit							128
Proceeds from Sale of Property, Plant, and Equipment	$ 5,500,000
Palo Alto [Member]
Subsequent Event [Line Items]
Long-term Purchase Commitment, Amount		$ 19,540,000
Debt Instrument, Interest Rate, Stated Percentage	5.80%	5.80%
TOB Facility [Member]
Subsequent Event [Line Items]
Debt financing	$ 137,200,000	$ 137,200,000				$ 124,700,000
Effective rate - minimum [Member]
Subsequent Event [Line Items]
Effective rate	3.40%	3.40%					4.70%
Effective rate - minimum [Member] | TOB Facility [Member]
Subsequent Event [Line Items]
Effective rate	2.80%	2.80%
Effective rate - maximum [Member]
Subsequent Event [Line Items]
Effective rate	9.50%	9.50%					8.30%
Effective rate - maximum [Member] | TOB Facility [Member]
Subsequent Event [Line Items]
Effective rate	4.50%	4.50%
Mortgage revenue bonds [Member]
Subsequent Event [Line Items]
Number of Units in Real Estate Property | Unit	7,332	7,332
Assets	$ 804,938,660	$ 804,938,660					$ 698,637,412
Mortgage revenue bonds [Member] | TEBS III Facility [Member] [Member]
Subsequent Event [Line Items]
Available for Sale Securities at Par Value	105,336,646	105,336,646			$ 105,356,928
Series B [Member] | TEBS III Facility [Member] [Member]
Subsequent Event [Line Items]
Mortgage revenue bonds held in trust, at fair value	$ 21,100,000	$ 21,100,000