Note 8 - Loans and Allowance for Loan Losses - Loans Individually Evaluated for Impairment (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Unpaid Contractual Principal Balance	$ 2,568,206	$ 2,252,362
Recorded Investment With No Allowance	2,036,040	1,701,000
Recorded Investment With Allowance	532,166	551,362
Impaired Financing Receivable, Recorded Investment, Total	2,568,206	2,252,362
Related Allowance	177,470	200,126
Average Recorded Investment	2,510,434	1,681,793
Residential Portfolio Segment [Member] \| One- to Four-family Loan [Member]
Unpaid Contractual Principal Balance	2,176,069	1,889,452
Recorded Investment With No Allowance	1,700,599	1,357,280
Recorded Investment With Allowance	475,470	532,172
Impaired Financing Receivable, Recorded Investment, Total	2,176,069	1,889,452
Related Allowance	154,520	190,531
Average Recorded Investment	2,153,496	1,298,425
Residential Portfolio Segment [Member] \| Multi-family Loans [Member]
Unpaid Contractual Principal Balance
Recorded Investment With No Allowance
Recorded Investment With Allowance
Impaired Financing Receivable, Recorded Investment, Total
Related Allowance
Average Recorded Investment
Nonresidential Real Estate Portfolio Segment [Member]
Unpaid Contractual Principal Balance	335,441	343,720
Recorded Investment With No Allowance	335,441	343,720
Recorded Investment With Allowance
Impaired Financing Receivable, Recorded Investment, Total	335,441	343,720
Related Allowance
Average Recorded Investment	338,039	377,632
Commercial Portfolio Segment [Member]
Unpaid Contractual Principal Balance
Recorded Investment With No Allowance
Recorded Investment With Allowance
Impaired Financing Receivable, Recorded Investment, Total
Related Allowance
Average Recorded Investment
Consumer Portfolio Segment [Member]
Unpaid Contractual Principal Balance	18,732
Recorded Investment With No Allowance
Recorded Investment With Allowance	18,732
Impaired Financing Receivable, Recorded Investment, Total	18,732
Related Allowance	3,968
Average Recorded Investment	6,244
Purchased Auto Loans [Member]
Unpaid Contractual Principal Balance	37,964	19,190
Recorded Investment With No Allowance
Recorded Investment With Allowance	37,964	19,190
Impaired Financing Receivable, Recorded Investment, Total	37,964	19,190
Related Allowance	18,982	9,595
Average Recorded Investment	$ 12,655	$ 5,736

Ottawa Bancorp Inc 10-Q