Variable Interest Entities Consolidating Balance Sheet (Details) (USD $)	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Assets [Abstract]
Cash and cash equivalents	$ 55,514,460		$ 20,176,906
Restricted cash	5,970,155		13,691,088
Interest receivable	9,124,124		6,984,978
Tax-exempt mortgage revenue bonds held in trust, at fair value	100,178,554		109,152,787
Tax-exempt mortgage revenue bonds, at fair value	38,623,510		26,542,565
Public housing capital fund trusts, at fair value	66,163,969		0
Real Estate Assets [Abstract]
Land	12,895,622		10,394,910
Buildings and improvements	112,488,768		103,911,079
Real estate assets before accumulated depreciation	125,384,390		114,305,989
Accumulated depreciation	(21,813,339)		(18,264,194)
Net real estate assets	103,571,051		96,041,795
Other assets	8,289,472		10,069,314
Assets of discontinued operations	8,224,333		15,317,112
Assets	395,659,628		297,976,545
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	3,660,766		3,231,360
Distribution payable	5,705,283		3,911,340
Debt financing	153,184,000		112,673,000
Mortgages payable	39,178,128		35,464,455
Liabilities of discontinued operations	4,870,902		11,107,345
Liabilities	206,599,079		166,387,500
General Partner	(367,578)		(354,006)
Beneficial Unit Certificate holders	213,005,840		154,911,228
Unallocated deficit of Consolidated VIEs	(24,525,004)		(23,512,962)
Total Partners' Capital	188,113,258	188,113,258	131,044,260
Noncontrolling interest	947,291		544,785
Total Capital	189,060,549		131,589,045	137,234,481	128,021,565
Total Liabilities and Partners' Capital	395,659,628		297,976,545
Partnership [Member]
Assets [Abstract]
Cash and cash equivalents	55,484,126		20,164,188
Restricted cash	4,693,511		12,754,035
Interest receivable	14,460,415		11,395,266
Tax-exempt mortgage revenue bonds held in trust, at fair value	125,004,792		132,920,723
Tax-exempt mortgage revenue bonds, at fair value	38,623,510		26,542,565
Public housing capital fund trusts, at fair value	66,163,969
Real Estate Assets [Abstract]
Land	8,523,403		7,144,866
Buildings and improvements	76,696,662		72,303,086
Real estate assets before accumulated depreciation	85,220,065		79,447,952
Accumulated depreciation	(8,404,483)		(5,931,860)
Net real estate assets	76,815,582		73,516,092
Other assets	23,349,351		20,080,854
Assets of discontinued operations	8,224,333		15,317,112
Assets	412,819,589		312,690,835
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	2,875,306		2,256,569
Distribution payable	5,705,283		3,911,340
Debt financing	153,184,000		112,673,000
Mortgages payable	39,178,128		35,464,455
Liabilities of discontinued operations	4,870,902		11,107,345
Liabilities	205,813,619		165,412,709
General Partner	(367,578)		(354,006)
Beneficial Unit Certificate holders	206,426,257		147,087,347
Unallocated deficit of Consolidated VIEs	0		0
Total Partners' Capital	206,058,679		146,733,341
Noncontrolling interest	947,291		544,785
Total Capital	207,005,970		147,278,126
Total Liabilities and Partners' Capital	412,819,589		312,690,835
Consolidated VIEs [Member]
Assets [Abstract]
Cash and cash equivalents	30,334		12,718
Restricted cash	1,276,644		937,053
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
Real Estate Assets [Abstract]
Land	4,372,219		3,250,044
Buildings and improvements	35,792,106		31,607,993
Real estate assets before accumulated depreciation	40,164,325		34,858,037
Accumulated depreciation	(13,408,856)		(12,332,334)
Net real estate assets	26,755,469		22,525,703
Other assets	672,562		839,879
Assets of discontinued operations	0		0
Assets	28,735,009		24,315,353
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	26,088,519		24,780,781
Distribution payable	0		0
Debt financing	0		0
Mortgages payable	24,221,000		24,407,000
Liabilities of discontinued operations	0		0
Liabilities	50,309,519		49,187,781
General Partner	0		0
Beneficial Unit Certificate holders	0		0
Unallocated deficit of Consolidated VIEs	(21,574,510)		(24,872,428)
Total Partners' Capital	(21,574,510)		(24,872,428)
Noncontrolling interest	0		0
Total Capital	(21,574,510)		(24,872,428)
Total Liabilities and Partners' Capital	28,735,009		24,315,353
Consolidations, Eliminations for VIEs [Member]
Assets [Abstract]
Cash and cash equivalents	0		0
Restricted cash	0		0
Interest receivable	(5,336,291)		(4,410,288)
Tax-exempt mortgage revenue bonds held in trust, at fair value	(24,826,238)		(23,767,936)
Tax-exempt mortgage revenue bonds, at fair value	0		0
Public housing capital fund trusts, at fair value	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	(15,732,441)		(10,851,419)
Assets of discontinued operations	0		0
Assets	(45,894,970)		(39,029,643)
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	(25,303,059)		(23,805,990)
Distribution payable	0		0
Debt financing	0		0
Mortgages payable	(24,221,000)		(24,407,000)
Liabilities of discontinued operations	0		0
Liabilities	(49,524,059)		(48,212,990)
General Partner	0		0
Beneficial Unit Certificate holders	6,579,583		7,823,881
Unallocated deficit of Consolidated VIEs	(2,950,494)		1,359,466
Total Partners' Capital	3,629,089		9,183,347
Noncontrolling interest	0		0
Total Capital	3,629,089		9,183,347
Total Liabilities and Partners' Capital	$ (45,894,970)		$ (39,029,643)