Note 3 - Debt Securities - Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized cost maturity:
Securities available for sale, due within one year, amortized cost	$ 19,970
Securities available for sale, due after one year but within five years, amortized cost	14,447
Securities available for sale, due after five years but within ten years, amortized cost	83,547
Securities available for sale, due after ten years, amortized cost
Securities available for sale, single maturity date, amortized cost	117,964
Securities available for sale, amortized cost	153,477	$ 164,290
Fair value maturity:
Securities available for sale, due within one year, fair value	19,960
Securities available for sale, due after one year but within five years, fair value	14,595
Securities available for sale, due after five years but within ten years, fair value	83,807
Securities available for sale, due after ten years, fair value
Securities available for sale, single maturity date, fair value	118,362
Securities available for sale	153,116	165,525	[1]
Held-to-maturity, Amortized cost maturity:
One year or less, amortized cost	25,013
After one year through five years, amortized cost
After five years through ten years, amortized cost
After ten years, amortized cost
Total amortized cost	25,013	25,149	[1]
Held-to-maturity, Fair value maturity:
One year or less	24,990
After one year through five years
After five years through ten years
After ten years
Total fair value	24,990	25,084
US Government Agencies Debt Securities [Member]
Amortized cost maturity:
Securities available for sale, due within one year, amortized cost
Securities available for sale, due after one year but within five years, amortized cost
Securities available for sale, due after five years but within ten years, amortized cost	1,108
Securities available for sale, due after ten years, amortized cost
Securities available for sale, single maturity date, amortized cost	1,108
Securities available for sale, amortized cost	1,108	11,289
Fair value maturity:
Securities available for sale, due within one year, fair value
Securities available for sale, due after one year but within five years, fair value
Securities available for sale, due after five years but within ten years, fair value	1,113
Securities available for sale, due after ten years, fair value
Securities available for sale, single maturity date, fair value	1,113
Securities available for sale	1,113	11,296
Held-to-maturity, Amortized cost maturity:
One year or less, amortized cost	17,887
After one year through five years, amortized cost
After five years through ten years, amortized cost
After ten years, amortized cost
Total amortized cost	17,887	17,937
Held-to-maturity, Fair value maturity:
One year or less	17,867
After one year through five years
After five years through ten years
After ten years
Total fair value	17,867	17,888
US Treasury Securities [Member]
Amortized cost maturity:
Securities available for sale, due within one year, amortized cost	19,970
Securities available for sale, due after one year but within five years, amortized cost
Securities available for sale, due after five years but within ten years, amortized cost
Securities available for sale, due after ten years, amortized cost
Securities available for sale, single maturity date, amortized cost	19,970
Securities available for sale, amortized cost	19,970	19,987
Fair value maturity:
Securities available for sale, due within one year, fair value	19,960
Securities available for sale, due after one year but within five years, fair value
Securities available for sale, due after five years but within ten years, fair value
Securities available for sale, due after ten years, fair value
Securities available for sale, single maturity date, fair value	19,960
Securities available for sale	19,960	19,971
US States and Political Subdivisions Debt Securities [Member]
Amortized cost maturity:
Securities available for sale, due within one year, amortized cost
Securities available for sale, due after one year but within five years, amortized cost	14,447
Securities available for sale, due after five years but within ten years, amortized cost	82,439
Securities available for sale, due after ten years, amortized cost
Securities available for sale, single maturity date, amortized cost	96,886
Securities available for sale, amortized cost	96,886	101,552
Fair value maturity:
Securities available for sale, due within one year, fair value
Securities available for sale, due after one year but within five years, fair value	14,595
Securities available for sale, due after five years but within ten years, fair value	82,694
Securities available for sale, due after ten years, fair value
Securities available for sale, single maturity date, fair value	97,289
Securities available for sale	97,289	103,648
Corporate Debt Securities [Member]
Held-to-maturity, Amortized cost maturity:
One year or less, amortized cost	7,126
After one year through five years, amortized cost
After five years through ten years, amortized cost
After ten years, amortized cost
Total amortized cost	7,126	7,212
Held-to-maturity, Fair value maturity:
One year or less	7,123
After one year through five years
After five years through ten years
After ten years
Total fair value	7,123	$ 7,196
Collateralized Mortgage Backed Securities [Member]
Amortized cost maturity:
Securities available for sale, no single maturity date, amortized cost	35,513
Fair value maturity:
Securities available for sale, no single maturity date, fair value	$ 34,754

[1] Derived from audited financial statements