Note 11 - Junior Subordinated Debt - Outstanding Payables (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Apr. 07, 2006
Principal amount			$ 20,619,000
Junior Subordinated Debt [Member]
Principal amount	$ 28,080,000	$ 28,029,000
Junior Subordinated Debt [Member] | AMNB Statutory Trust I [Member]
Principal amount	20,619,000	20,619,000
Junior Subordinated Debt [Member] | MidCarolina Trust I [Member]
Principal amount	4,461,000	4,433,000
Junior Subordinated Debt [Member] | MidCarolina Trust II [Member]
Principal amount	$ 3,000,000	$ 2,977,000
London Interbank Offered Rate (LIBOR) [Member] | Junior Subordinated Debt [Member] | AMNB Statutory Trust I [Member]
Interest rate	1.35%
London Interbank Offered Rate (LIBOR) [Member] | Junior Subordinated Debt [Member] | MidCarolina Trust I [Member]
Interest rate	3.45%
London Interbank Offered Rate (LIBOR) [Member] | Junior Subordinated Debt [Member] | MidCarolina Trust II [Member]
Interest rate	2.95%