Condensed Consolidated Statements of Partners' Capital (Unaudited) - USD ($)	Total	Tier 2 [Member]	General Partner [Member]	General Partner [Member] Tier 2 [Member]	BUCs - Restricted and Unrestricted [Member]	BUCs - Restricted and Unrestricted [Member] Tier 2 [Member]	Number of BUCs - Restricted and Unrestricted [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2019	$ 341,938,263		$ 735,128		$ 341,203,135			$ 99,308,677
Partners' Capital Account, Units at Dec. 31, 2019							60,835,204
Distributions paid or accrued:
Regular distribution	(8,050,119)		(80,501)		(7,969,618)
Distribution of Tier 2 (income) loss (Note 3)		$ 445,719		$ 80,501		$ 365,218
Net income (loss) allocable to Partners	2,263,994		(53,404)		2,317,398
Repurchase of BUCs, Value	(2,106,673)				(2,106,673)
Repurchase of BUCs, Units							(290,000)
Restricted units awarded							290,000
Restricted unit compensation expense	39,068		391		38,677
Unrealized loss on securities	(7,057,736)		(70,577)		(6,987,159)			(7,057,736)
Reversal of net unrealized gains on sale of securities	(1,408,804)		(14,088)		(1,394,716)			(1,408,804)
Reversal of net unrealized loss on securities to provision for credit loss	372,169		3,722		368,447			372,169
Balance at Mar. 31, 2020	326,435,881		601,172		325,834,709			91,214,306
Partners' Capital Account, Units at Mar. 31, 2020							60,835,204
Balance at Dec. 31, 2020	359,772,042		934,892		358,837,150			132,594,007
Partners' Capital Account, Units at Dec. 31, 2020							60,823,674
Distributions paid or accrued:
Regular distribution	(3,401,314)		(34,013)		(3,367,301)
Distribution of Tier 2 (income) loss (Note 3)		$ (2,809,106)		$ (702,277)		$ (2,106,829)
Net income (loss) allocable to Partners	6,275,091		736,936		5,538,155
Restricted unit compensation expense	78,114		781		77,333
Unrealized loss on securities	(16,298,797)		(162,988)		(16,135,809)			(16,298,797)
Unrealized loss on bond purchase commitments	(120,970)		(1,210)		(119,760)			(120,970)
Balance at Mar. 31, 2021	$ 343,495,060		$ 772,121		$ 342,722,939			$ 116,174,240
Partners' Capital Account, Units at Mar. 31, 2021							60,823,674