Note 11 - Long-term Borrowings - Junior Subordinated Debt Outstanding Payables (Details) - USD ($)		12 Months Ended
	Sep. 30, 2011	Dec. 31, 2021	Dec. 31, 2020	Apr. 07, 2006
Principal amount				$ 20,619,000
Principal amount				$ 20,619,000
Junior Subordinated Debt [Member]
Principal amount		$ 28,232,000	$ 28,130,000
Principal amount		28,232,000	28,130,000
Junior Subordinated Debt [Member] | AMNB Statutory Trust I [Member]
Principal amount		20,619,000	20,619,000
Principal amount		20,619,000	20,619,000
Junior Subordinated Debt [Member] | MidCarolina Trust I [Member]
Principal amount		4,545,000	4,489,000
Principal amount		4,545,000	4,489,000
Junior Subordinated Debt [Member] | MidCarolina Trust II [Member]
Principal amount		3,068,000	3,022,000
Principal amount		$ 3,068,000	$ 3,022,000
London Interbank Offered Rate (LIBOR) [Member] | Junior Subordinated Debt [Member]
Interest rate	1.35%
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%