Investments in Mortgage Revenue Bonds Narrative Tagging (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($) Integer Unit	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Integer Unit	Sep. 30, 2014 USD ($)	Sep. 30, 2016	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Mortgage revenue bonds, at fair value		$ 28,247,980		$ 28,247,980					$ 70,601,045
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities				22,323,371	$ 6,665,718
Property loans receivable		24,995,110		24,995,110					22,191,515
Unrecognized Tax Benefits, Interest on Income Taxes Accrued				2,782,579	1,906,569
Provision for loss on receivables		0	$ 75,000	0	75,000
Payments to Acquire Available-for-sale Securities				$ 137,805,000	107,770,827
Number of Available for Sale Securities | Integer				53
Loans Payable		19,161,532		$ 19,161,532					15,990,439
Available-for-sale Securities, Amortized Cost Basis, Held in Trust		454,875,266		454,875,266					338,861,752
Cost adjusted for pay-downs		25,193,081		25,193,081					65,538,068
Available-For-Sale Securities, Gross Unrealized Loss MTM		25,958		25,958					19,582
Mortgage revenue bonds held in trust, at fair value		499,197,562		499,197,562					378,423,092
Proceeds from Sale of Available-for-sale Securities				0	35,483,230
Available-for-sale Securities, Gross Realized Gain (Loss)				(630,919)	(2,413,713)
Debt financing		$ 447,606,493		$ 447,606,493					345,359,000
Adverse change rate		10.00%		10.00%
10% unrealized loss				$ 32,300,000
Silver Moon [Member]
Number of Units in Real Estate Property | Unit		151		151
Property loans receivable		$ 2,813,452		$ 2,813,452
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Loans Payable		$ 2,819,183		$ 2,819,183
Renaissance Gateway [Member]
Number of Units in Real Estate Property | Unit		208		208
Perrin Square [Member]
Number of Units in Real Estate Property | Unit		236		236
Concord at Gulfgate [Member]
Number of Units in Real Estate Property | Unit		288		288
Heritage Square [Member]
Mortgage revenue bonds, at fair value									12,814,125
Cost adjusted for pay-downs									11,705,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									0
Bruton Apartments [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]	$ 18,145,000		$ 18,145,000
Mortgage revenue bonds held in trust, at fair value	[1]	19,648,516		19,648,516
Live 929 Apartments [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]	40,822,598		40,822,598					40,895,739
Mortgage revenue bonds held in trust, at fair value	[1]	45,085,222		45,085,222					44,693,484
Decatur-Angle [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]	23,000,000		23,000,000					23,000,000
Mortgage revenue bonds held in trust, at fair value	[1]	24,094,952		24,094,952					23,919,540
Lost Creek [Member]
Proceeds from Sale of Available-for-sale Securities					$ 18,700,000
Copper Gate [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	5,220,000		5,220,000					5,220,000
Mortgage revenue bonds held in trust, at fair value	[2]	5,764,237		5,764,237					5,783,656
The Palms at Premier Park [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	20,043,237		20,043,237					20,152,000
Mortgage revenue bonds held in trust, at fair value	[2]	$ 22,156,072		$ 22,156,072					22,832,619
The Suites on Paseo [Member]
Number of Units in Real Estate Property | Unit		394		394
Cash Received for Accrued Investment Income Receivable							$ 500,000
Accrued Investment Income Receivable							674,000
Property loans receivable		$ 1,100,000		$ 1,100,000			$ 567,340
Real Estate Investment Property, at Cost		43,400,000		43,400,000
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]								35,450,000
Mortgage revenue bonds held in trust, at fair value	[1]								38,643,691
Seasons at Simi Valley [Member]
Mortgage revenue bonds, at fair value		$ 6,539,709		$ 6,539,709
Number of Units in Real Estate Property | Unit		69		69
Cost adjusted for pay-downs		$ 6,320,000		$ 6,320,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		$ 0		$ 0
Vantage at Harlingen [Member]
Mortgage revenue bonds, at fair value									7,399,813
Soft Interest Rate		3.00%		3.00%
Number of Units in Real Estate Property | Unit		288		288
Soft Interest Income				$ 330,000
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Cost adjusted for pay-downs									6,692,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									0
Greens of Pine Glen [Member]
Property loans receivable		$ 850,000		$ 850,000					850,000
Loans Payable		1,230,981		1,230,981					1,081,342
Rennaisance [Member]
Mortgage revenue bonds, at fair value									13,730,807
Cost adjusted for pay-downs									12,675,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									0
Avistar Portfolio [Member]
Property loans receivable		274,496		274,496					274,496
Loans Payable		$ 317,153		$ 317,153					290,966
Vantage at Judson [Member]
Mortgage revenue bonds, at fair value									6,766,230
Soft Interest Rate		3.00%		3.00%
Number of Units in Real Estate Property | Unit		288		288
Soft Interest Income				$ 446,000
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Cost adjusted for pay-downs									6,049,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									0
Concord at Little York [Member]
Number of Units in Real Estate Property | Unit		276		276
Concord at Williamcrest [Member]
Number of Units in Real Estate Property | Unit		288		288
Concord Portfolio [Member]
TOB Financing		$ 41,800,000		$ 41,800,000
Number of Available for Sale Securities, Held in a Trust | Integer		3		3
Series A and B [Member] | The Suites on Paseo [Member]
Mortgage revenue bonds, at fair value		$ 41,000,000		$ 41,000,000
Series A-1 [Member] | Seasons at Simi Valley [Member]
Mortgage revenue bonds, at fair value		$ 4,400,000		$ 4,400,000
Debt Instrument, Maturity Date				Sep. 01, 2032
Debt Instrument, Interest Rate, Stated Percentage		5.75%		5.75%
Series A-2 [Member] | Seasons at Simi Valley [Member]
Mortgage revenue bonds, at fair value		$ 1,900,000		$ 1,900,000
Debt Instrument, Maturity Date				Sep. 01, 2017
Debt Instrument, Interest Rate, Stated Percentage		5.50%		5.50%		8.00%
Series A [Member] | Silver Moon [Member]
Debt Instrument, Maturity Date				Aug. 01, 2055
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[3]	$ 7,995,983		$ 7,995,983
Cost adjusted for pay-downs		8,000,000		8,000,000
Mortgage revenue bonds held in trust, at fair value	[3]	$ 9,060,239		$ 9,060,239
Series A [Member] | Renaissance Gateway [Member]
Debt Instrument, Maturity Date				Jun. 01, 2050
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[3]	$ 11,475,663		$ 11,475,663
Cost adjusted for pay-downs		11,500,000		11,500,000				$ 8,500,000
Mortgage revenue bonds held in trust, at fair value	[3]	$ 12,483,132		$ 12,483,132
Series A [Member] | Perrin Square [Member]
Debt Instrument, Maturity Date				May 01, 2052
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[3]	$ 13,300,000		$ 13,300,000
Cost adjusted for pay-downs		13,300,000		13,300,000
Mortgage revenue bonds held in trust, at fair value	[3]	13,381,808		13,381,808
Series A [Member] | Concord at Gulfgate [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]	17,060,000		17,060,000
Cost adjusted for pay-downs		17,100,000		17,100,000
Mortgage revenue bonds held in trust, at fair value	[1]	17,922,126		17,922,126
Series A [Member] | Heritage Square [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[3]	11,185,000		11,185,000
Mortgage revenue bonds held in trust, at fair value	[3]	11,252,782		11,252,782
Series A [Member] | Harden Ranch [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	6,960,000		6,960,000					6,960,000
Mortgage revenue bonds held in trust, at fair value	[2]	7,531,277		7,531,277					7,471,421
Series A [Member] | Tyler Park Apartments [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	6,075,000		6,075,000					6,075,000
Mortgage revenue bonds held in trust, at fair value	[2]	6,478,195		6,478,195					6,420,060
Series A [Member] | Westside Village Market [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	3,970,000		3,970,000					3,970,000
Mortgage revenue bonds held in trust, at fair value	[2]	4,233,487		4,233,487					4,195,496
Series A [Member] | Greens of Pine Glen [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	8,312,000		8,312,000					8,366,000
Mortgage revenue bonds held in trust, at fair value	[2]	9,295,623		9,295,623					9,371,119
Series A [Member] | Avistar on the Boulevard [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	16,454,530		16,454,530					16,525,000
Mortgage revenue bonds held in trust, at fair value	[2]	18,002,749		18,002,749					18,943,599
Series A [Member] | Avistar at Chase Hill [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	9,957,357		9,957,357					10,000,000
Mortgage revenue bonds held in trust, at fair value	[2]	11,098,255		11,098,255					11,196,800
Series A [Member] | Avistar at the Crest [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[2]	9,658,636		9,658,636					9,700,000
Mortgage revenue bonds held in trust, at fair value	[2]	10,765,307		10,765,307					11,119,692
Series A [Member] | Concord at Little York [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]	12,480,000		12,480,000
Cost adjusted for pay-downs		12,500,000		12,500,000
Mortgage revenue bonds held in trust, at fair value	[1]	13,110,743		13,110,743
Series A [Member] | Concord at Williamcrest [Member]
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[1]	18,020,000		18,020,000
Cost adjusted for pay-downs		18,000,000		18,000,000
Mortgage revenue bonds held in trust, at fair value	[1]	$ 18,930,663		$ 18,930,663
Series A [Member] | Concord Portfolio [Member]
Debt Instrument, Maturity Date				Feb. 01, 2032
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Series B [Member] | Silver Moon [Member]
Debt Instrument, Interest Rate, Stated Percentage		12.00%		12.00%
Cost adjusted for pay-downs		$ 500,000		$ 500,000
Series B [Member] | Renaissance Gateway [Member]
Cost adjusted for pay-downs								1,300,000
Series B [Member] | Perrin Square [Member]
Mortgage revenue bonds, at fair value		$ 155,042		$ 155,042
Debt Instrument, Maturity Date				Jun. 01, 2052
Debt Instrument, Interest Rate, Stated Percentage		12.00%		12.00%
Cost adjusted for pay-downs		$ 125,000		$ 125,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		0		0
Series B [Member] | Concord at Gulfgate [Member]
Mortgage revenue bonds, at fair value		2,738,794		2,738,794
Cost adjusted for pay-downs		2,125,000		2,125,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		0		0
Series B [Member] | Heritage Square [Member]
Mortgage revenue bonds, at fair value		644,101		644,101
Cost adjusted for pay-downs		520,000		520,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		$ 0		0
Series B [Member] | Harden Ranch [Member]
Mortgage revenue bonds, at fair value									2,338,499
Cost adjusted for pay-downs									2,340,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									1,501
Series B [Member] | Tyler Park Apartments [Member]
Mortgage revenue bonds, at fair value									2,007,605
Cost adjusted for pay-downs									2,025,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									17,395
Series B [Member] | Westside Village Market [Member]
Mortgage revenue bonds, at fair value									1,429,314
Cost adjusted for pay-downs									1,430,000
Available-For-Sale Securities, Gross Unrealized Loss MTM									686
Series B [Member] | Harden Ranch, Tyler Park and Westside Village [Member]
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities				$ 5,800,000
Series B [Member] | Vantage at Harlingen [Member]
Debt Instrument, Maturity Date				Sep. 01, 2053
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[3]	$ 24,575,000		$ 24,575,000
Cost adjusted for pay-downs		24,600,000		24,600,000
Mortgage revenue bonds held in trust, at fair value	[3]	26,180,115		26,180,115
Series B [Member] | Greens of Pine Glen [Member]
Mortgage revenue bonds, at fair value		1,197,341		1,197,341					1,321,841
Cost adjusted for pay-downs		943,847		943,847					945,638
Available-For-Sale Securities, Gross Unrealized Loss MTM		0		0					0
Series B [Member] | Avistar on the Boulevard [Member]
Mortgage revenue bonds, at fair value		494,036		494,036					524,851
Cost adjusted for pay-downs		450,070		450,070					451,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		0		0					0
Series B [Member] | Avistar at Chase Hill [Member]
Mortgage revenue bonds, at fair value		1,057,083		1,057,083					1,109,769
Cost adjusted for pay-downs		963,011		963,011					965,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		0		0					0
Series B [Member] | Avistar at the Crest [Member]
Mortgage revenue bonds, at fair value		831,427		831,427					883,286
Cost adjusted for pay-downs		757,434		757,434					759,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		$ 0		$ 0					$ 0
Series B [Member] | Vantage at Judson [Member]
Debt Instrument, Maturity Date				Jan. 01, 2053
Debt Instrument, Interest Rate, Stated Percentage		6.00%		6.00%
Available-for-sale Securities, Amortized Cost Basis, Held in Trust	[3]	$ 26,540,000		$ 26,540,000
Cost adjusted for pay-downs		26,500,000		26,500,000
Mortgage revenue bonds held in trust, at fair value	[3]	29,168,931		29,168,931
Series B [Member] | Concord at Little York [Member]
Mortgage revenue bonds, at fair value		1,212,621		1,212,621
Cost adjusted for pay-downs		960,000		960,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		0		0
Series B [Member] | Concord at Williamcrest [Member]
Mortgage revenue bonds, at fair value		3,372,669		3,372,669
Cost adjusted for pay-downs		2,800,000		2,800,000
Available-For-Sale Securities, Gross Unrealized Loss MTM		$ 0		$ 0
Series B [Member] | Concord Portfolio [Member]
Debt Instrument, Maturity Date				Mar. 01, 2032
Debt Instrument, Interest Rate, Stated Percentage		12.00%		12.00%
Series C [Member] | Renaissance Gateway [Member]
Cost adjusted for pay-downs		$ 1,200,000		$ 1,200,000				$ 1,700,000
Series C [Member] | Vantage at Harlingen [Member]
Cost adjusted for pay-downs		6,700,000		6,700,000
Series C [Member] | Vantage at Judson [Member]
Cost adjusted for pay-downs		$ 6,000,000		$ 6,000,000
Series D [Member] | Vantage at Harlingen [Member]
Debt Instrument, Maturity Date				Apr. 01, 2035
Debt Instrument, Interest Rate, Stated Percentage		9.00%		9.00%
Cost adjusted for pay-downs		$ 1,300,000		$ 1,300,000
Series D [Member] | Vantage at Judson [Member]
Debt Instrument, Maturity Date				Jan. 01, 2053
Debt Instrument, Interest Rate, Stated Percentage		9.00%		9.00%
Cost adjusted for pay-downs		$ 900,000		$ 900,000
Effective rate - maximum [Member]
Effective rate		9.50%		9.50%					8.30%
Effective rate - minimum [Member]
Effective rate		3.40%		3.40%					4.70%
10% adverse [Member] | Effective rate - maximum [Member]
Effective rate		10.50%		10.50%
10% adverse [Member] | Effective rate - minimum [Member]
Effective rate		3.70%		3.70%
TOB Facility-1 [Member]
Debt, Weighted Average Interest Rate		1.10%		1.10%
Mortgage revenue bonds [Member]
Debt, Weighted Average Interest Rate		6.20%		6.20%
Number of Units in Real Estate Property | Unit		7,332		7,332
Trading Securities [Member]
Debt financing		$ 193,155,000		$ 193,155,000					$ 174,250,000
CALIFORNIA
Percentage of Available for Sale Securities by Location		10.00%		10.00%					18.00%
TEXAS
Percentage of Available for Sale Securities by Location		54.00%		54.00%					38.00%

[1] Mortgage revenue bonds held by Deutsche Bank in a secured financing transaction, see Note 11

[2] Mortgage revenue bonds owned by ATAX TEBS II, LLC, see Note 11(4) Mortgage revenue bonds owned by ATAX TEBS III, LLC, see Note 11

[3] Mortgage revenue bonds owned by ATAX TEBS III, LLC, see Note 11