Fair Value of Financial Instruments - Summary of Activity Related to Level 3 Assets and Liabilities (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($)		3 Months Ended				6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017		Jan. 01, 2018
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value, beginning balance		$ 810,176,708		$ 820,480,265		$ 843,675,611		$ 742,897,488
Assets at Fair Value, Adjusted balance										$ 843,458,663
Total gains (losses) (realized/unrealized) [Abstract]
Total gain (losses) included in earnings (interest income and interest expense)		(807,729)		(142,314)		199,306		(227,896)
Total gain (losses) included in other comprehensive (loss) income		4,014,225		10,771,467		(18,835,718)		29,972,777
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		19,540,000		496,800		19,540,000		60,081,800
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(11,972,562)		(1,350,194)		(23,411,609)		(2,468,145)
Assets at Fair Value, ending balance		820,950,642		830,256,024		820,950,642		830,256,024
Total amount of gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to assets or liabilities held		(824,676)		(181,420)		165,319		(302,769)
Interest rate derivatives [Member]
Schedule of Available-for-sale Securities [Line Items]
Liabilities at Fair value, beginning balance		852,702	[1]	(1,077,028)	[1]			(955,679)	[2]
Liabilities at Fair value, Adjusted balance	[1]									(229,631)
Total gains (losses) (realized/unrealized) [Abstract]
Total gain (losses) included in earnings (interest income and interest expense)		6,386	[1]	(181,420)	[1]	996,381	[1]	(302,769)	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				496,800	[1]			496,800	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[1]	38,870				131,208
Liabilities at Fair value, ending balance	[1]	897,958		(761,648)	[2]	897,958		(761,648)	[2]
Total amount of gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to assets or liabilities held		6,386	[1]	(181,420)	[1]	996,381	[1]	(302,769)	[2]
Bond Purchase Commitment [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value, beginning balance		2,027,473		2,620,393		3,002,540		2,399,449
Assets at Fair Value, Adjusted balance										3,002,540
Total gains (losses) (realized/unrealized) [Abstract]
Total gain (losses) included in other comprehensive (loss) income		(1,032,788)		544,779		(2,007,855)		765,723
Assets at Fair Value, ending balance		994,685		3,165,172		994,685		3,165,172
Public housing capital fund trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value, beginning balance		48,939,254		55,851,799		49,641,588		57,158,068
Assets at Fair Value, Adjusted balance										49,641,588
Total gains (losses) (realized/unrealized) [Abstract]
Total gain (losses) included in earnings (interest income and interest expense)		(850,336)		(14,129)		(869,610)		(31,717)
Total gain (losses) included in other comprehensive (loss) income		981,792		390,701		525,446		(897,980)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements				(437,000)		(226,714)		(437,000)
Assets at Fair Value, ending balance		49,070,710		55,791,371		49,070,710		55,791,371
Total amount of gains (losses) for the period included in earnings attributable to the change in unrealized gains (losses) relating to assets or liabilities held		(831,062)				(831,062)
Taxable Mortgage Revenue Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value, beginning balance		2,397,825		4,179,205		2,422,459		4,084,599
Assets at Fair Value, Adjusted balance										2,422,459
Total gains (losses) (realized/unrealized) [Abstract]
Total gain (losses) included in other comprehensive (loss) income		(12,079)		(223,758)		(33,981)		(125,264)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(27,794)		(23,976)		(30,526)		(27,864)
Assets at Fair Value, ending balance		2,357,952		3,931,471		2,357,952		3,931,471
Mortgage Revenue Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value, beginning balance	[3]	755,959,454		758,905,896				680,211,051
Assets at Fair Value, Adjusted balance	[4]									$ 788,621,707
Total gains (losses) (realized/unrealized) [Abstract]
Total gain (losses) included in earnings (interest income and interest expense)		36,221	[3]	53,235	[3]	72,535	[4]	106,590	[3]
Total gain (losses) included in other comprehensive (loss) income		4,077,300	[3]	10,059,745	[3]	(17,319,328)	[4]	30,230,298	[3]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		19,540,000	[3]			19,540,000	[4]	59,585,000	[3]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(11,983,638)	[3]	(889,218)	[3]	(23,285,577)	[4]	(2,003,281)	[3]
Assets at Fair Value, ending balance	[3]	$ 767,629,337	[4]	$ 768,129,658		$ 767,629,337	[4]	$ 768,129,658

[1] Interest rate derivatives include derivative contracts reported in other assets as well as derivative swap liabilities.

[2] Interest rate derivatives include derivative contracts reported in other assets as well as derivative swap liabilities

[3] Mortgage revenue bonds includes both bonds held in trust as well as those held by the Partnership.

[4] Mortgage revenue bonds includes both bonds held in trust as well as those held by the Partnership. The beginning balance also in includes the cumulative effect of accounting change related to the adoption of ASU 2017-08 effective January 1, 2018.