Commitments and Contingencies - Summary of outstanding loan commitments, unused lines of credit and letters of credit (Details) - USD ($)
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Loan commitments      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability $ 970,000 $ 1,666,000 $ 4,378,000
Construction and land development      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability 1,561,000
Other mortgage loans      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability $ 970,000 $ 1,666,000 2,817,000
Unused lines of credit      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability 20,415,509 19,706,092 19,490,826
Home-equity lines      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability 2,558,091 3,825,462 11,067,236
Commercial lines      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability 17,195,796 15,156,201 7,726,424
Secured consumer line      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability 27,500 50,000 24,043
Unsecured consumer lines      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability 634,122 674,429 673,123
Letters of credit      
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]      
Fair value disclosure, off-balance sheet risks, face amount, liability $ 47,580 $ 57,580 $ 32,000