Fair Value of Financial Instruments - Carrying Value and Estimated Fair Value of Financial Instruments (Detail) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Financial assets
Cash and due from banks	$ 12,641,231	$ 17,962,990
Interest bearing deposits with banks	1,293,179	1,532,420
Securities available-for-sale	463,752,185	505,046,377
Net loans	413,544,127	401,706,081
Financial liabilities
Deposits	764,674,148	720,821,564
Federal Funds Purchase	12,500,000	1,500,000
Federal Home Loan Bank advances	20,000,000	30,005,541
Securities Sold under Agreement to Repurchase	74,124,947	142,497,938
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Cash and due from banks	12,641,231	17,962,990
Interest bearing deposits with banks	1,293,179	1,532,420
Financial liabilities
Deposits		543,123,284
Federal Funds Purchase	12,500,000
Securities Sold under Agreement to Repurchase		142,497,938
Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Securities available-for-sale	463,752,185	501,972,150
Financial liabilities
Deposits	764,674,148
Federal Home Loan Bank advances	20,000,000
Securities Sold under Agreement to Repurchase	74,124,947
Significant Unobservable Inputs (Level 3) [Member]
Financial assets
Securities available-for-sale		3,074,227
Net loans	413,544,127	401,706,081
Financial liabilities
Deposits		177,698,280
Federal Home Loan Bank advances		30,005,541
Carrying Value [Member]
Financial assets
Cash and due from banks	12,641,231	17,962,990
Interest bearing deposits with banks	1,293,179	1,532,420
Securities available-for-sale	463,752,185	505,046,377
Net loans	417,589,558	402,390,574
Financial liabilities
Deposits	764,610,980	720,685,499
Federal Funds Purchase	12,500,000
Federal Home Loan Bank advances	20,000,000	30,000,000
Securities Sold under Agreement to Repurchase	$ 74,124,947	$ 142,497,938