LOAN PORTFOLIO COMPOSITION - Impaired Loans (Details 4) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Balance, Total	$ 4,518,075	$ 4,443,559	$ 3,071,672
Unpaid Principal Balance, Total	4,518,075	4,443,559	3,071,672
Specific Allowance, Total	918,907	1,219,238	926,367
Average Impairment in Impaired Loans, Total	4,611,739	4,655,901	3,755,335
Interest Income Recognized, Total	61,983	59,887	186,119
Interest Income Recognized Cash Basis, Total	57,258	74,151	192,497
Real estate loans \| One-to-four family residential
Financing Receivable, Impaired [Line Items]
Loans without a specific valuation allowance, Recorded Balance	212,908	231,961	223,997
Loans without a specific valuation allowance, Unpaid Principal Balance	212,908	231,961	223,997
Loans without a specific valuation allowance, Average Impairment in Impaired Loans	217,436	265,795	244,463
Loans without a specific valuation allowance, Interest Income Recognized	2,834	3,563	12,789
Loans without a specific valuation allowance, Interest Income Recognized Cash Basis	2,886	3,713	12,771
Loans with a specific valuation allowance, Recorded Balance	941,316	496,333	439,369
Loans with a specific valuation allowance, Unpaid Principal Balance	941,316	496,333	439,369
Loans with a specific valuation allowance, Specific Allowance	224,993	251,976	176,635
Loans with a specific valuation allowance, Average Impairment in Impaired Loans	951,131	499,324	434,203
Loans with a specific valuation allowance, Interest Income Recognized	12,372	6,350	21,596
Loans with a specific valuation allowance, Interest Income Recognized Cash Basis	12,023	5,076	20,823
Recorded Balance, Total	1,154,224	728,294	663,366
Unpaid Principal Balance, Total	1,154,224	728,294	663,366
Specific Allowance, Total	224,993	251,976	176,635
Average Impairment in Impaired Loans, Total	1,168,567	765,119	678,666
Interest Income Recognized, Total	15,206	9,913	34,385
Interest Income Recognized Cash Basis, Total	14,909	8,789	33,594
Real estate loans \| Commercial real estate
Financing Receivable, Impaired [Line Items]
Loans without a specific valuation allowance, Recorded Balance	838,443	1,053,432	444,500
Loans without a specific valuation allowance, Unpaid Principal Balance	838,443	1,053,432	444,500
Loans without a specific valuation allowance, Average Impairment in Impaired Loans	835,880	1,053,606	951,010
Loans without a specific valuation allowance, Interest Income Recognized	12,795	14,552	41,732
Loans without a specific valuation allowance, Interest Income Recognized Cash Basis	11,067	19,933	40,184
Loans with a specific valuation allowance, Recorded Balance	967,859	1,711,659	990,222
Loans with a specific valuation allowance, Unpaid Principal Balance	967,859	1,711,659	990,222
Loans with a specific valuation allowance, Specific Allowance	451,367	894,407	472,393
Loans with a specific valuation allowance, Average Impairment in Impaired Loans	1,040,249	1,740,514	1,071,991
Loans with a specific valuation allowance, Interest Income Recognized	14,765	22,022	61,601
Loans with a specific valuation allowance, Interest Income Recognized Cash Basis	14,984	20,011	63,773
Recorded Balance, Total	1,806,302	2,765,091	1,434,722
Unpaid Principal Balance, Total	1,806,302	2,765,091	1,434,722
Specific Allowance, Total	451,367	894,407	472,393
Average Impairment in Impaired Loans, Total	1,876,129	2,794,120	2,023,001
Interest Income Recognized, Total	27,560	36,574	103,333
Interest Income Recognized Cash Basis, Total	26,051	39,944	103,957
Real estate loans \| Home equity
Financing Receivable, Impaired [Line Items]
Loans without a specific valuation allowance, Recorded Balance	46,629	52,541	43,683
Loans without a specific valuation allowance, Unpaid Principal Balance	46,629	52,541	43,683
Loans without a specific valuation allowance, Average Impairment in Impaired Loans	47,404	53,321	52,350
Loans without a specific valuation allowance, Interest Income Recognized	844	893	3,617
Loans without a specific valuation allowance, Interest Income Recognized Cash Basis	796	790	3,393
Recorded Balance, Total	46,629	52,541	43,683
Unpaid Principal Balance, Total	46,629	52,541	43,683
Specific Allowance, Total	0	0	0
Average Impairment in Impaired Loans, Total	47,404	53,321	52,350
Interest Income Recognized, Total	844	893	3,617
Interest Income Recognized Cash Basis, Total	796	790	3,393
Commercial
Financing Receivable, Impaired [Line Items]
Loans without a specific valuation allowance, Recorded Balance	1,111,970	411,682	421,049
Loans without a specific valuation allowance, Unpaid Principal Balance	1,111,970	411,682	421,049
Loans without a specific valuation allowance, Average Impairment in Impaired Loans	1,094,363	535,531	473,657
Loans without a specific valuation allowance, Interest Income Recognized	12,940	6,732	24,123
Loans without a specific valuation allowance, Interest Income Recognized Cash Basis	4,828	5,924	23,768
Loans with a specific valuation allowance, Recorded Balance	129,416	106,644	132,901
Loans with a specific valuation allowance, Unpaid Principal Balance	129,416	106,644	132,901
Loans with a specific valuation allowance, Specific Allowance	129,416	62,059	132,901
Loans with a specific valuation allowance, Average Impairment in Impaired Loans	145,514	112,152	145,858
Loans with a specific valuation allowance, Interest Income Recognized	2,274	975	2,608
Loans with a specific valuation allowance, Interest Income Recognized Cash Basis	3,125	391	1,545
Recorded Balance, Total	1,241,386	518,326	553,950
Unpaid Principal Balance, Total	1,241,386	518,326	553,950
Specific Allowance, Total	129,416	62,059	132,901
Average Impairment in Impaired Loans, Total	1,239,877	647,683	619,515
Interest Income Recognized, Total	15,214	7,707	26,731
Interest Income Recognized Cash Basis, Total	7,953	6,315	25,313
Agricultural
Financing Receivable, Impaired [Line Items]
Loans with a specific valuation allowance, Recorded Balance	269,534	379,307	375,951
Loans with a specific valuation allowance, Unpaid Principal Balance	269,534	379,307	375,951
Loans with a specific valuation allowance, Specific Allowance	113,131	10,796	144,438
Loans with a specific valuation allowance, Average Impairment in Impaired Loans	279,762	395,658	381,803
Loans with a specific valuation allowance, Interest Income Recognized	3,159	4,800	18,053
Loans with a specific valuation allowance, Interest Income Recognized Cash Basis	7,549	18,313	26,240
Recorded Balance, Total	269,534	379,307	375,951
Unpaid Principal Balance, Total	269,534	379,307	375,951
Specific Allowance, Total	113,131	10,796	144,438
Average Impairment in Impaired Loans, Total	279,762	395,658	381,803
Interest Income Recognized, Total	3,159	4,800	18,053
Interest Income Recognized Cash Basis, Total	$ 7,549	$ 18,313	$ 26,240

Jacksonville Bancorp, Inc. 10-Q