Condensed Consolidated Statements of Partners' Capital (Unaudited) - USD ($)	Total	General Partner [Member]	Beneficial Unit Certificate Holders [Member]	Beneficial Unit Certificate Holders - Restricted and Unrestricted [Member]	Number of Units [Member]	Number of Units - Restricted and Unrestricted [Member]	Noncontrolling Interest [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2015	$ 313,124,827	$ 399,077	$ 312,720,264				$ 5,486	$ 60,963,687
Partners' Capital Account, Units at Dec. 31, 2015					60,252,928
Reversal of net unrealized gain on sale of securities	(236,439)	(2,364)	(234,075)					(236,439)
Distributions paid or accrued
Regular distribution	(7,607,693)	(76,077)	(7,531,616)
Net income (loss) allocated to Partners and noncontrolling interests:
Redeemable Series A Preferred Unit distribution accrued and accretion	(1,684)	(17)	(1,667)
Net income (loss) allocable to Partners	2,530,004
Net income (loss)	2,531,688	67,172	2,464,528				(12)	2,531,688
Unrealized gain on securities	12,337,427	123,374	12,214,053					12,337,427
Unrealized gain on bond purchase commitments	1,587,813	15,878	1,571,935					1,587,813
Balance at Mar. 31, 2016	321,735,939	527,043	$ 321,203,422				5,474	74,652,488
Partners' Capital Account, Units at Mar. 31, 2016					60,252,928
Balance at Dec. 31, 2016	280,133,868	102,536		$ 280,026,669			4,663	38,895,484
Partners' Capital Account, Units at Dec. 31, 2016						60,224,538
Distribution to noncontrolling interest	(76,316)						(76,316)
Distributions paid or accrued
Regular distribution	(4,261,023)	(42,610)		(4,218,413)
Distribution of Tier 2 earnings (Note 3)	(4,417,604)	(1,104,401)		(3,313,203)
Net income (loss) allocated to Partners and noncontrolling interests:
Net income (loss) allocable to Partners	7,035,873	1,147,072		5,817,148			$ 71,653
Net income (loss)	7,360,515							7,360,515
Repurchase of Beneficial Unit Certificates	(823,358)			(823,358)
Repurchase of Beneficial Unit Certificates, Units						(144,748)
Restricted units awarded						173,138
Restricted units compensation expense	170,840	1,708		169,132
Unrealized gain on securities	18,980,366	189,804		18,790,562				18,980,366
Unrealized gain on bond purchase commitments	220,944	2,209		218,735				220,944
Balance at Mar. 31, 2017	$ 296,963,590	$ 296,318		$ 296,667,272				$ 58,096,794
Partners' Capital Account, Units at Mar. 31, 2017						60,252,928