Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	$ 820,480,265	$ 742,897,488
Bond Purchase Commitments (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	2,620,393	2,399,449
PHC Certificates [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	55,851,799	57,158,068
Taxable Bonds (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	4,179,205	4,084,599
Derivative Contracts (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	151,730	383,604
Derivative Swap Liability [Member]
Schedule of Available-for-sale Securities [Line Items]
Liabilities at fair value	(1,228,758)	(1,339,283)
Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	820,480,265	742,897,488	$ 666,958,282	$ 653,875,949
Fair Value, Inputs, Level 3 [Member] | Bond Purchase Commitments (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,620,393	2,399,449	7,222,173	5,634,360
Fair Value, Inputs, Level 3 [Member] | PHC Certificates [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	55,851,799	57,158,068	60,505,340	60,707,290
Fair Value, Inputs, Level 3 [Member] | Taxable Bonds (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	4,179,205	4,084,599	$ 4,938,104	$ 4,824,060
Fair Value, Inputs, Level 3 [Member] | Derivative Contracts (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	151,730	383,604
Fair Value, Inputs, Level 3 [Member] | Derivative Swap Liability [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liabilities Value	(1,228,758)	(1,339,283)
Mortgage Revenue Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	27,814,516	90,016,872
Mortgage Revenue Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	27,814,516	90,016,872
Mortgage Revenue Bonds Held In Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	731,091,380	590,194,179
Mortgage Revenue Bonds Held In Trust [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 731,091,380	$ 590,194,179