Variable Interest Entities Consolidating Balance Sheet (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Assets [Abstract]
Cash and cash equivalents	$ 13,336,312	$ 30,172,773
Restricted cash	4,595,649	5,471,522
Interest receivable	10,851,898	8,473,360
Tax-exempt mortgage revenue bonds held in trust, at fair value	130,391,760	99,534,082
Tax-exempt mortgage revenue bonds, at fair value	76,467,415	45,703,294
Public housing capital fund trusts, at fair value	64,613,713	65,389,298
Available-for-sale Securities, Fair Value Disclosure, Mortgage-backed Securities	34,115,328	32,121,412
Real Estate Assets [Abstract]
Land	11,221,298	11,202,876
Buildings and improvements	96,004,727	93,615,479
Real estate assets before accumulated depreciation	107,226,025	104,818,355
Accumulated depreciation	(20,519,236)	(19,330,063)
Net real estate assets	86,706,789	85,488,292
Other assets	11,004,379	8,216,295
Assets of discontinued operations	9,963,239	32,580,427
Assets	442,046,482	413,150,755
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	5,445,866	5,013,947
Distribution payable	5,400,621	5,566,908
Debt financing	194,267,900	177,948,000
Mortgages payable	46,558,021	39,119,507
Liabilities of discontinued operations	115,668	1,531,462
Liabilities	251,788,076	229,179,824
Partners' Capital
General Partner	69,728	(430,087)
Beneficial Unit Certificate holders	214,252,021	207,383,087
Unallocated deficit of Consolidated VIEs	(25,276,767)	(25,035,808)
Total Partners' Capital	189,044,982	181,917,192	189,044,982
Noncontrolling interest	1,213,424	2,053,739
Total Capital	190,258,406	183,970,931		131,589,045
Total Liabilities and Partners' Capital	442,046,482	413,150,755
Partnership [Member]
Assets [Abstract]
Cash and cash equivalents	13,312,928	30,123,447
Restricted cash	3,690,160	4,538,071
Interest receivable	16,837,415	14,131,063
Tax-exempt mortgage revenue bonds held in trust, at fair value	155,347,034	124,149,600
Tax-exempt mortgage revenue bonds, at fair value	76,467,415	45,703,294
Public housing capital fund trusts, at fair value	64,613,713	65,389,298
Available-for-sale Securities, Fair Value Disclosure, Mortgage-backed Securities	34,115,328	32,121,412
Real Estate Assets [Abstract]
Land	7,971,254	6,798,407
Buildings and improvements	64,014,909	55,776,753
Real estate assets before accumulated depreciation	71,986,163	62,575,160
Accumulated depreciation	(6,450,506)	(5,458,961)
Net real estate assets	65,535,657	57,116,199
Other assets	19,850,322	22,923,356
Assets of discontinued operations	9,963,239	32,580,427
Assets	459,733,211	428,776,167
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	4,558,345	2,330,852
Distribution payable	5,400,621	5,566,908
Debt financing	194,267,900	177,948,000
Mortgages payable	46,558,021	39,119,507
Liabilities of discontinued operations	115,668	1,531,462
Liabilities	250,900,555	226,496,729
Partners' Capital
General Partner	69,728	(430,087)
Beneficial Unit Certificate holders	207,549,504	200,655,786
Unallocated deficit of Consolidated VIEs	0	0
Total Partners' Capital	207,619,232	200,225,699
Noncontrolling interest	1,213,424	2,053,739
Total Capital	208,832,656	202,279,438
Total Liabilities and Partners' Capital	459,733,211	428,776,167
Consolidated VIEs [Member]
Assets [Abstract]
Cash and cash equivalents	23,384	49,326
Restricted cash	905,489	933,451
Interest receivable	0	0
Tax-exempt mortgage revenue bonds held in trust, at fair value	0	0
Tax-exempt mortgage revenue bonds, at fair value	0	0
Public housing capital fund trusts, at fair value	0	0
Available-for-sale Securities, Fair Value Disclosure, Mortgage-backed Securities	0	0
Real Estate Assets [Abstract]
Land	3,250,044	4,404,469
Buildings and improvements	31,989,818	37,838,726
Real estate assets before accumulated depreciation	35,239,862	42,243,195
Accumulated depreciation	(14,068,730)	(13,871,102)
Net real estate assets	21,171,132	28,372,093
Other assets	735,448	852,321
Assets of discontinued operations	0	0
Assets	22,835,453	30,207,191
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	27,214,033	28,529,405
Distribution payable	0	0
Debt financing	0	0
Mortgages payable	24,092,000	24,158,000
Liabilities of discontinued operations	0	0
Liabilities	51,306,033	52,687,405
Partners' Capital
General Partner	0	0
Beneficial Unit Certificate holders	0	0
Unallocated deficit of Consolidated VIEs	(28,470,580)	(22,480,214)
Total Partners' Capital	(28,470,580)	(22,480,214)
Noncontrolling interest	0	0
Total Capital	(28,470,580)	(22,480,214)
Total Liabilities and Partners' Capital	22,835,453	30,207,191
Consolidations, Eliminations for VIEs [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	0	0
Interest receivable	(5,985,517)	(5,657,703)
Tax-exempt mortgage revenue bonds held in trust, at fair value	(24,955,274)	(24,615,518)
Tax-exempt mortgage revenue bonds, at fair value	0	0
Public housing capital fund trusts, at fair value	0	0
Available-for-sale Securities, Fair Value Disclosure, Mortgage-backed Securities	0	0
Real Estate Assets [Abstract]
Land	0	0
Buildings and improvements	0	0
Real estate assets before accumulated depreciation	0	0
Accumulated depreciation	0	0
Net real estate assets	0	0
Other assets	(9,581,391)	(15,559,382)
Assets of discontinued operations	0	0
Assets	(40,522,182)	(45,832,603)
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	(26,326,512)	(25,846,310)
Distribution payable	0	0
Debt financing	0	0
Mortgages payable	(24,092,000)	(24,158,000)
Liabilities of discontinued operations	0	0
Liabilities	(50,418,512)	(50,004,310)
Partners' Capital
General Partner	0	0
Beneficial Unit Certificate holders	6,702,517	6,727,301
Unallocated deficit of Consolidated VIEs	3,193,813	(2,555,594)
Total Partners' Capital	9,896,330	4,171,707
Noncontrolling interest	0	0
Total Capital	9,896,330	4,171,707
Total Liabilities and Partners' Capital	$ (40,522,182)	$ (45,832,603)