Fair Value Measurements Available for sale securities (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure			$ 137,018,622
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	667,821	0	667,821	0
Deconsolidation of VIE			0	9,996,003	1,861,051
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities			95,000	0
Assets, Fair Value Disclosure	137,389,392		137,389,392		137,018,622
Tax-exempt mortgage revenue bonds [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	136,846,619		136,846,619		135,695,352
Interest rate derivatives [Member]
Total gains (lossses) (realized/unrealized) [Abstract]
Assets, Fair Value Disclosure	542,773		542,773		1,323,270
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	139,570,108	111,101,801	137,018,622	103,973,434	103,973,434
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	(451,157)	(656,000)	(780,497)	(888,554)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	4,047,983	3,790,432	6,889,571	6,639,472
Deconsolidation of VIE		15,810,000		15,083,757
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	10,164,815	15,625,000	10,164,815	20,117,500
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	(15,625,000)	(5,795,000)	(15,625,000)	(5,047,208)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(317,357)	(52,188)	(278,119)	(54,356)
Assets, Fair Value Disclosure	137,389,392	139,824,045	137,389,392	139,824,045
Fair Value, Inputs, Level 3 [Member] | Tax-exempt mortgage revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	138,576,178	107,927,564	135,695,352	100,566,643	100,566,643
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	0	0	0	0
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities	4,047,983	3,790,432	6,889,571	6,639,472
Deconsolidation of VIE		15,810,000		15,083,757
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	10,164,815	15,625,000	10,164,815	20,117,500
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	(15,625,000)	(5,795,000)	(15,625,000)	(5,047,208)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(317,357)	(52,188)	(278,119)	(54,356)
Assets, Fair Value Disclosure	136,846,619	137,305,808	136,846,619	137,305,808
Fair Value, Inputs, Level 3 [Member] | Interest rate derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Fair Value Disclosure	993,930	3,174,237	1,323,270	3,406,791	3,406,791
Total gains (lossses) (realized/unrealized) [Abstract]
Gain (Loss) on Investments	(451,157)	(656,000)	(780,497)	(888,554)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities		0	0	0
Deconsolidation of VIE		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0	0
Assets, Fair Value Disclosure	$ 542,773	$ 2,518,237	$ 542,773	$ 2,518,237