Fair Value Measurements Available for sale securities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			$ 535,793,465
Total gains (lossses) (realized/unrealized) [Abstract]
Gain on sale and retirement of bonds	$ 0	$ 0	0	$ 3,684,898
Assets, Fair Value Disclosure	609,270,389		609,270,389
Mortgage revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			449,024,137
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	527,445,542		527,445,542
Bond Purchase Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			5,780,413
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	3,335,926		3,335,926
Public housing capital fund trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			61,263,123
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	59,876,842		59,876,842
Trust Portfolio--MBS Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			14,841,558
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	14,681,587		14,681,587
Taxable Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			4,616,565
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	5,056,428		5,056,428
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			267,669
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	(1,125,936)		(1,125,936)
Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		$ 0
Fair Value, Inputs, Level 1 [Member] | Mortgage revenue bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		0
Fair Value, Inputs, Level 1 [Member] | Bond Purchase Commitment [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		0
Fair Value, Inputs, Level 1 [Member] | Public housing capital fund trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		0
Fair Value, Inputs, Level 1 [Member] | Trust Portfolio--MBS Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		0
Fair Value, Inputs, Level 1 [Member] | Taxable Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		0
Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity Method Investment, Quoted Market Value	0		0		0
Fair Value, Inputs, Level 2 [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	14,681,587		14,681,587		14,841,558
Fair Value, Inputs, Level 2 [Member] | Mortgage revenue bonds [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	0		0		0
Fair Value, Inputs, Level 2 [Member] | Bond Purchase Commitment [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	0		0		0
Fair Value, Inputs, Level 2 [Member] | Public housing capital fund trusts [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	0		0		0
Fair Value, Inputs, Level 2 [Member] | Trust Portfolio--MBS Bonds [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	14,681,587		14,681,587		14,841,558
Fair Value, Inputs, Level 2 [Member] | Taxable Bonds [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	0		0		0
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Assets [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value Observable inputs (level 2)	0		0		0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	613,079,147	426,684,885	520,951,907	347,486,446
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	(1,254,563)	(153,810)	(1,955,693)	(763,718)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	22,919,296	19,957,822	(61,576)	55,343,528
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	6,320,000	31,115,700	138,305,000	107,770,827
Mortgage Revenue Bond Exchanged for MF Property	(40,950,000)		(40,950,000)
Refund of Interest Rate Derivative Cost			(10,500)
Gain on sale and retirement of bonds		991,400		(30,464,798)
Deriviative at purchase price	572,588		572,588	1,382,900
Assets, Fair Value Disclosure	594,588,802	474,346,921	594,588,802	474,346,921
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(6,097,666)	(4,249,076)	(22,262,924)	(6,408,264)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	594,588,802		594,588,802		520,951,907
Fair Value, Inputs, Level 3 [Member] | Mortgage revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	548,935,985	356,313,065	449,024,137	285,318,171
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	0	0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	19,222,410	17,464,986	2,752,871	42,498,644
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	6,320,000	31,115,700	137,805,000	107,770,827
Mortgage Revenue Bond Exchanged for MF Property	(40,950,000)		(40,950,000)
Refund of Interest Rate Derivative Cost			0
Gain on sale and retirement of bonds		0		(30,464,798)
Deriviative at purchase price	0		0	0
Assets, Fair Value Disclosure	527,445,542	404,789,122	527,445,542	404,789,122
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(6,082,853)	(104,629)	(21,186,466)	(333,722)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	527,445,542		527,445,542		449,024,137
Fair Value, Inputs, Level 3 [Member] | Bond Purchase Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	883,999	334,367	5,780,413	(4,852,177)
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	0	0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	2,451,927	2,634,574	(2,444,487)	7,821,118
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	$ 0	0	0	0
Mortgage Revenue Bond Exchanged for MF Property			0
Refund of Interest Rate Derivative Cost			0
Gain on sale and retirement of bonds		0		0
Deriviative at purchase price	$ 0		0	0
Assets, Fair Value Disclosure	3,335,926	2,968,941	3,335,926	2,968,941
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3,335,926		3,335,926		5,780,413
Fair Value, Inputs, Level 3 [Member] | Public housing capital fund trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	58,991,437	64,997,718	61,263,123	62,056,379
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	0	0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	899,057	(316,185)	(381,802)	4,480,249
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	$ 0	0	0	0
Mortgage Revenue Bond Exchanged for MF Property			0
Refund of Interest Rate Derivative Cost			0
Gain on sale and retirement of bonds		0		0
Deriviative at purchase price	$ 0		0	0
Assets, Fair Value Disclosure	59,876,842	60,537,086	59,876,842	60,537,086
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(13,652)	(4,144,447)	(1,004,479)	(5,999,542)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	59,876,842		59,876,842		61,263,123
Fair Value, Inputs, Level 3 [Member] | Trust Portfolio--MBS Bonds [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0		0		0
Fair Value, Inputs, Level 3 [Member] | Taxable Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	4,711,687	4,370,023	4,616,565	4,075,953
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	0	0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	345,902	174,447	11,842	543,517
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	$ 0	0	500,000	0
Mortgage Revenue Bond Exchanged for MF Property			0
Refund of Interest Rate Derivative Cost			0
Gain on sale and retirement of bonds		0		0
Deriviative at purchase price	$ 0		0	0
Assets, Fair Value Disclosure	5,056,428	4,544,470	5,056,428	4,544,470
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(1,161)	0	(71,979)	(75,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	5,056,428		5,056,428		4,616,565
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	(443,961)	669,712	267,669	888,120
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	(1,254,563)	(153,810)	(1,955,693)	(763,718)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	$ 0	0	0	0
Mortgage Revenue Bond Exchanged for MF Property			0
Refund of Interest Rate Derivative Cost			(10,500)
Gain on sale and retirement of bonds		991,400		0
Deriviative at purchase price	$ 572,588		572,588	1,382,900
Assets, Fair Value Disclosure	(1,125,936)	1,507,302	(1,125,936)	1,507,302
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	$ 0	0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ (1,125,936)		$ (1,125,936)		$ 267,669