Note 4 - Investment Securities - Expected Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Less than one year, Available for sale, Amortized Cost	$ 116,110	$ 115,445
Less than one year, Available for sale, Estimated Fair Value	115,954	115,464
More than one year to five years, Available for sale, Amortized Cost	145,207	34,869
Available for sale, Estimated Fair Value, More than one year to five years	144,884	35,607
More than five years to ten years, Available for sale, Amortized Cost	67,049	53,328
More than five years to ten years, Available for sale, Estimated Fair Value	67,214	54,128
More than ten years, Available for sale, Amortized Cost	17,399	5,621
More than ten years, Available for sale, Estimated Fair Value	16,948	5,668
Available for sale, amortized cost	345,765	209,263
Available for sale	345,000	210,867
Less than one year, Held to Maturity, Amortized Cost	500	899
Held to maturity, Estimated Fair Value	502	910
More than one year to five years, Held to maturity, Amortized Cost	1,006	1,508
More than one year to five years, Held to Maturity, Estimated Fair Value	1,099	1,636
More than five years to ten years, Held to maturity Amortized Cost	1,745	874
More than five years to ten years, Held to Maturity, Estimated Fair Value	1,823	925
More than ten years, Held to Maturity, Amortized Cost	3,007	3,893
More than ten years, Held to Maturity, Estimated Fair Value	3,174	4,132
Held to maturity (fair value of $6,598 and $7,603 at September 30, 2021 and December 31, 2020, respectively)	6,258	7,174
Securities held to maturity, fair value	6,598	7,603
US Government Agencies Debt Securities [Member]
Less than one year, Available for sale, Amortized Cost	0	0
Less than one year, Available for sale, Estimated Fair Value	0	0
More than one year to five years, Available for sale, Amortized Cost	748	1,257
Available for sale, Estimated Fair Value, More than one year to five years	761	1,294
More than five years to ten years, Available for sale, Amortized Cost	0	0
More than five years to ten years, Available for sale, Estimated Fair Value	0	0
More than ten years, Available for sale, Amortized Cost	0	0
More than ten years, Available for sale, Estimated Fair Value	0	0
Available for sale, amortized cost	748	1,257
Available for sale	761	1,294
Small Business Administration Agency Securities [Member]
Less than one year, Available for sale, Amortized Cost	0	0
Less than one year, Available for sale, Estimated Fair Value	0	0
More than one year to five years, Available for sale, Amortized Cost	1,041	595
Available for sale, Estimated Fair Value, More than one year to five years	1,080	625
More than five years to ten years, Available for sale, Amortized Cost	2,608	3,530
More than five years to ten years, Available for sale, Estimated Fair Value	2,745	3,769
More than ten years, Available for sale, Amortized Cost	0	0
More than ten years, Available for sale, Estimated Fair Value	0	0
Available for sale, amortized cost	3,649	4,125
Available for sale	3,825	4,394
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than one year, Available for sale, Amortized Cost	5,001	7,992
Less than one year, Available for sale, Estimated Fair Value	4,998	7,987
More than one year to five years, Available for sale, Amortized Cost	47,553	9,423
Available for sale, Estimated Fair Value, More than one year to five years	47,443	9,690
More than five years to ten years, Available for sale, Amortized Cost	7,944	0
More than five years to ten years, Available for sale, Estimated Fair Value	7,810	0
More than ten years, Available for sale, Amortized Cost	0	0
More than ten years, Available for sale, Estimated Fair Value	0	0
Available for sale, amortized cost	60,498	17,415
Available for sale	60,251	17,677
Collateralized Mortgage Obligations [Member]
Less than one year, Available for sale, Amortized Cost	150	0
Less than one year, Available for sale, Estimated Fair Value	153	0
More than one year to five years, Available for sale, Amortized Cost	89,563	11,911
Available for sale, Estimated Fair Value, More than one year to five years	89,132	12,258
More than five years to ten years, Available for sale, Amortized Cost	36,116	36,565
More than five years to ten years, Available for sale, Estimated Fair Value	36,026	36,616
More than ten years, Available for sale, Amortized Cost	0	0
More than ten years, Available for sale, Estimated Fair Value	0	0
Available for sale, amortized cost	125,829	48,476
Available for sale	125,311	48,874
Commercial Paper [Member]
Less than one year, Available for sale, Amortized Cost	99,963	102,462
Less than one year, Available for sale, Estimated Fair Value	99,784	102,448
More than one year to five years, Available for sale, Amortized Cost	0	0
Available for sale, Estimated Fair Value, More than one year to five years	0	0
More than five years to ten years, Available for sale, Amortized Cost	0	0
More than five years to ten years, Available for sale, Estimated Fair Value	0	0
More than ten years, Available for sale, Amortized Cost	0	0
More than ten years, Available for sale, Estimated Fair Value	0	0
Available for sale, amortized cost	99,963	102,462
Available for sale	99,784	102,448
Corporate Debt Securities [Member]
Less than one year, Available for sale, Amortized Cost	10,996	4,991
Less than one year, Available for sale, Estimated Fair Value	11,019	5,029
More than one year to five years, Available for sale, Amortized Cost	6,302	11,683
Available for sale, Estimated Fair Value, More than one year to five years	6,468	11,740
More than five years to ten years, Available for sale, Amortized Cost	20,381	13,233
More than five years to ten years, Available for sale, Estimated Fair Value	20,633	13,743
More than ten years, Available for sale, Amortized Cost	4,690	4,000
More than ten years, Available for sale, Estimated Fair Value	4,612	4,051
Available for sale, amortized cost	42,369	33,907
Available for sale	42,732	34,563
Municipal Bonds [Member]
Less than one year, Available for sale, Amortized Cost	0	0
Less than one year, Available for sale, Estimated Fair Value	0	0
More than one year to five years, Available for sale, Amortized Cost	0	0
Available for sale, Estimated Fair Value, More than one year to five years	0	0
More than five years to ten years, Available for sale, Amortized Cost	0	0
More than five years to ten years, Available for sale, Estimated Fair Value	0	0
More than ten years, Available for sale, Amortized Cost	12,709	1,621
More than ten years, Available for sale, Estimated Fair Value	12,336	1,617
Available for sale, amortized cost	12,709	1,621
Available for sale	12,336	1,617
Less than one year, Held to Maturity, Amortized Cost	0	0
Held to maturity, Estimated Fair Value	0	0
More than one year to five years, Held to maturity, Amortized Cost	0	0
More than one year to five years, Held to Maturity, Estimated Fair Value	0	0
More than five years to ten years, Held to maturity Amortized Cost	1,745	874
More than five years to ten years, Held to Maturity, Estimated Fair Value	1,823	925
More than ten years, Held to Maturity, Amortized Cost	3,007	3,893
More than ten years, Held to Maturity, Estimated Fair Value	3,174	4,132
Held to maturity (fair value of $6,598 and $7,603 at September 30, 2021 and December 31, 2020, respectively)	4,752	4,767
Securities held to maturity, fair value	4,997	5,057
Taxable Municipal Bonds [Member]
Less than one year, Held to Maturity, Amortized Cost	500	899
Held to maturity, Estimated Fair Value	502	910
More than one year to five years, Held to maturity, Amortized Cost	1,006	1,508
More than one year to five years, Held to Maturity, Estimated Fair Value	1,099	1,636
More than five years to ten years, Held to maturity Amortized Cost	0	0
More than five years to ten years, Held to Maturity, Estimated Fair Value	0	0
More than ten years, Held to Maturity, Amortized Cost	0	0
More than ten years, Held to Maturity, Estimated Fair Value	0	0
Held to maturity (fair value of $6,598 and $7,603 at September 30, 2021 and December 31, 2020, respectively)	1,506	2,407
Securities held to maturity, fair value	$ 1,601	$ 2,546