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Commitments and Contingencies Fair Market Value Table (Details) - USD ($)
3 Months Ended
Mar. 31, 2017
Dec. 31, 2016
Maximum Committed Amounts for 2017    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Purchase Commitment, Amount $ 30,540,000  
Maximum Committed Amounts for 2018    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Purchase Commitment, Amount 16,400,000  
Bond Purchase Commitment [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Unrealized Gain $ 2,620,393 $ 2,399,449
Villas at Plano Gateway [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Forward Bond Commitment, Purchase Date Dec. 31, 2014  
Debt Instrument, Interest Rate, Stated Percentage 6.00%  
Villas at Plano Gateway [Member] | Bond Purchase Commitment [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Unrealized Gain   838,200
Village at River's Edge [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Forward Bond Commitment, Purchase Date May 31, 2015  
Debt Instrument, Interest Rate, Stated Percentage 6.00%  
Village at River's Edge [Member] | Maximum Committed Amounts for 2017    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Purchase Commitment, Amount $ 11,000,000  
Village at River's Edge [Member] | Bond Purchase Commitment [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Unrealized Gain $ 643,720 467,720
Palo Alto [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Forward Bond Commitment, Purchase Date Jul. 31, 2015  
Debt Instrument, Interest Rate, Stated Percentage 5.80%  
Palo Alto [Member] | Maximum Committed Amounts for 2017    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Purchase Commitment, Amount $ 19,540,000  
Palo Alto [Member] | Bond Purchase Commitment [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Unrealized Gain $ 1,116,320 627,429
Village at Avalon [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Forward Bond Commitment, Purchase Date Nov. 30, 2015  
Debt Instrument, Interest Rate, Stated Percentage 5.80%  
Village at Avalon [Member] | Maximum Committed Amounts for 2018    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Purchase Commitment, Amount $ 16,400,000  
Village at Avalon [Member] | Bond Purchase Commitment [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Unrealized Gain $ 860,353 $ 466,100