Note 2 - Mergers and Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($)	Jan. 01, 2019	Jan. 31, 2018	Jun. 30, 2019	Dec. 31, 2018
Goodwill			$ 15,710,000	$ 12,124,000
Big Muddy Bancorp Acquisition [Member]
Cash and cash equivalents	$ 6,902,000
Investment securities	2,096,000
Loans	89,204,000
Premises and equipment	2,246,000
Cash surrender value of life insurance	2,862,000
Other real estate owned	223,000
Core deposit intangible	1,988,000
Other assets	1,995,000
Total assets acquired	107,516,000
Deposits	92,706,000
Accrued expenses and other liabilities	1,960,000
Total liabilities assumed	94,666,000
Net assets acquired	12,850,000
Cash	1,000
Common stock issued (996,041 shares BMB and 446,774 shares TwinCo)	16,435,000
Total consideration paid	16,436,000
Goodwill	$ 3,586,000
TwinCo Acquisition [Member]
Cash and cash equivalents		$ 5,657,000
Investment securities		30,728,000
Loans		55,057,000
Premises and equipment		1,605,000
Cash surrender value of life insurance
Other real estate owned		135,000
Core deposit intangible		1,609,000
Other assets		1,258,000
Total assets acquired		96,049,000
Deposits		82,190,000
Accrued expenses and other liabilities		19,000
Total liabilities assumed		82,209,000
Net assets acquired		13,840,000
Cash		9,900,000
Common stock issued (996,041 shares BMB and 446,774 shares TwinCo)		9,030,000
Total consideration paid		18,930,000
Goodwill		$ 5,090,000