Note 3 - Investment Securities - Summary of Investment Securities Available-for-sale and Regulatory Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investment securities available-for-sale, amortized cost	$ 162,174	$ 134,731
Investment securities available-for-sale, gross unrealized gains	5,461	2,007
Investment securities available-for-sale, gross unrealized losses	58	607
Investment securities available-for-sale, fair value	167,577	136,131
Federal Home Loan Bank (FHLB) stock	2,805	2,609
Federal Home Loan Bank (FHLB) stock	2,805	2,609
Federal Reserve Bank (FRB) stock	226	226
Federal Reserve Bank (FRB) stock	226	226
Regulatory stock (Note 3)	3,031	2,835
Total regulatory stock	3,031	2,835
US Government Corporations and Agencies Securities [Member]
Investment securities available-for-sale, amortized cost	0	3,348
Investment securities available-for-sale, gross unrealized gains	0	1
Investment securities available-for-sale, gross unrealized losses	0	39
Investment securities available-for-sale, fair value	0	3,310
US States and Political Subdivisions Debt Securities [Member]
Investment securities available-for-sale, amortized cost	84,264	67,794
Investment securities available-for-sale, gross unrealized gains	4,174	1,853
Investment securities available-for-sale, gross unrealized losses	27	21
Investment securities available-for-sale, fair value	88,411	69,626
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment securities available-for-sale, amortized cost	66,929	48,566
Investment securities available-for-sale, gross unrealized gains	1,014	75
Investment securities available-for-sale, gross unrealized losses	28	404
Investment securities available-for-sale, fair value	67,915	48,237
Collateralized Mortgage Obligations [Member]
Investment securities available-for-sale, amortized cost	5,507	8,447
Investment securities available-for-sale, gross unrealized gains	112	78
Investment securities available-for-sale, gross unrealized losses	3	44
Investment securities available-for-sale, fair value	5,616	8,481
US Government Small Business Administration Securities [Member]
Investment securities available-for-sale, amortized cost	5,474	6,576
Investment securities available-for-sale, gross unrealized gains	161	0
Investment securities available-for-sale, gross unrealized losses	0	99
Investment securities available-for-sale, fair value	$ 5,635	$ 6,477

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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