Note 4 - Loans and the Allowance for Credit Losses - Loan Portfolio Allocated by Internal Risk Ratings (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Year one	$ 32,421		$ 164,713
Year two	169,550		225,826
Year three	224,591		139,988
Year four	133,129		110,395
Year five	107,708		65,010
Before five years prior	230,666		176,034
Revolving loans	77,983		76,233
Revolving loans converted to term loan	3,250		3,272
Total, gross	979,298		961,471
Year one, write off	0		0
Year three, write off	308		642
Year four, write off	46		260
Total, gross, write off	680		1,802
Year two, write off	129		471
Year five, write off	65		267
Before five years prior, write off	132		135
Revolving loans, write off	0		27
Revolving loans converted to term loan, write off	0		0
Performing Financial Instruments [Member]
Year one	876		34,291
Year two	31,747		33,267
Year three	30,758		16,965
Year four	15,409		8,806
Year five	7,773		6,386
Before five years prior	8,237		3,704
Revolving loans	144		159
Revolving loans converted to term loan	0		0
Total, gross	94,944		103,578
Nonperforming Financial Instruments [Member]
Year one	0		167
Year two	101		232
Year three	106		179
Year four	191		210
Year five	199		228
Before five years prior	191		37
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	788		1,053
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Year one	7,017		15,549
Year two	16,166		20,527
Year three	19,604		12,194
Year four	11,668		3,812
Year five	3,331		4,322
Before five years prior	9,108		5,257
Revolving loans	15,952		13,272
Revolving loans converted to term loan	0		0
Total, gross	82,846		74,933
Year one, write off	0		0
Year three, write off	43		40
Year four, write off			14
Total, gross, write off	43	$ (0)	123
Year two, write off			34
Year five, write off			0
Before five years prior, write off			10
Revolving loans, write off			25
Revolving loans converted to term loan, write off			0
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Pass [Member]
Year one	7,017		15,549
Year two	16,166		18,995
Year three	18,484		11,603
Year four	11,085		3,472
Year five	3,003		4,291
Before five years prior	8,990		5,165
Revolving loans	15,678		13,079
Revolving loans converted to term loan	0		0
Total, gross	80,423		72,154
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Special Mention [Member]
Year one	0		0
Year two	0		0
Year three	0		302
Year four	295		0
Year five	0		31
Before five years prior	65		68
Revolving loans	252		170
Revolving loans converted to term loan	0		0
Total, gross	612		571
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Substandard [Member]
Year one	0		0
Year two	0		1,532
Year three	1,120		289
Year four	288		340
Year five	328		0
Before five years prior	53		24
Revolving loans	22		23
Revolving loans converted to term loan	0		0
Total, gross	1,811		2,208
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Year one	3,326		20,106
Year two	15,855		25,073
Year three	24,304		14,354
Year four	16,079		16,567
Year five	16,236		12,263
Before five years prior	32,890		21,769
Revolving loans	14,833		19,546
Revolving loans converted to term loan	0		0
Total, gross	123,523		129,678
Year one, write off	0		0
Year three, write off	0		0
Year four, write off	0		0
Total, gross, write off	0	(0)	0
Year two, write off	0		0
Year five, write off	0		0
Before five years prior, write off	0		0
Revolving loans, write off	0		0
Revolving loans converted to term loan, write off	0		0
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Pass [Member]
Year one	2,169		12,028
Year two	10,104		17,382
Year three	16,712		13,182
Year four	12,909		15,550
Year five	14,907		11,495
Before five years prior	30,165		20,704
Revolving loans	14,410		18,925
Revolving loans converted to term loan	0		0
Total, gross	101,376		109,266
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Special Mention [Member]
Year one	1,157		1,852
Year two	1,525		813
Year three	755		97
Year four	95		1,017
Year five	1,329		16
Before five years prior	1,726		817
Revolving loans	423		621
Revolving loans converted to term loan	0		0
Total, gross	7,010		5,233
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Substandard [Member]
Year one	0		6,226
Year two	4,226		6,878
Year three	6,837		1,075
Year four	3,075		0
Year five	0		752
Before five years prior	999		248
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	15,137		15,179
Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Year one	19,724		74,595
Year two	78,747		115,902
Year three	120,252		90,436
Year four	83,976		76,881
Year five	76,767		40,609
Before five years prior	173,382		139,545
Revolving loans	10,247		6,246
Revolving loans converted to term loan	0		0
Total, gross	563,095		544,214
Year one, write off	0		0
Year three, write off	0		0
Year four, write off	0		0
Total, gross, write off	0	(0)	0
Year two, write off	0		0
Year five, write off	0		0
Before five years prior, write off	0		0
Revolving loans, write off	0		0
Revolving loans converted to term loan, write off	0		0
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Pass [Member]
Year one	19,724		74,595
Year two	78,747		115,890
Year three	120,241		90,436
Year four	83,976		76,401
Year five	76,403		40,256
Before five years prior	167,887		133,958
Revolving loans	10,247		6,246
Revolving loans converted to term loan	0		0
Total, gross	557,225		537,782
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Special Mention [Member]
Year one	0		0
Year two	0		0
Year three	0		0
Year four	0		199
Year five	94		0
Before five years prior	2,843		3,316
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	2,937		3,515
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Substandard [Member]
Year one	0		0
Year two	0		12
Year three	11		0
Year four	0		281
Year five	270		353
Before five years prior	2,652		2,271
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	2,933		2,917
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Year one	1,478		18,878
Year two	25,813		30,825
Year three	29,567		3,717
Year four	3,681		1,672
Year five	976		619
Before five years prior	882		281
Revolving loans	1,764		1,368
Revolving loans converted to term loan	0		0
Total, gross	64,161		57,360
Year one, write off	0		0
Year three, write off	0		0
Year four, write off	0		0
Total, gross, write off	0	(0)	0
Year two, write off	0		0
Year five, write off	0		0
Before five years prior, write off	0		0
Revolving loans, write off	0		0
Revolving loans converted to term loan, write off	0		0
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Pass [Member]
Year one	1,478		18,878
Year two	25,813		30,825
Year three	29,567		3,717
Year four	3,681		1,672
Year five	976		619
Before five years prior	882		281
Revolving loans	1,764		1,368
Revolving loans converted to term loan	0		0
Total, gross	64,161		57,360
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Special Mention [Member]
Year one	0
Year two	0
Year three	0
Year four	0
Year five	0
Before five years prior	0
Revolving loans	0
Revolving loans converted to term loan	0
Total, gross	0
Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Year one	0		1,127
Year two	1,121		0
Year three	0		2,143
Year four	2,125		2,447
Year five	2,426		583
Before five years prior	5,976		5,441
Revolving loans	252		201
Revolving loans converted to term loan	0		0
Total, gross	11,900		11,942
Year one, write off	0		0
Year three, write off	0		0
Year four, write off	0		0
Total, gross, write off	0	(0)	0
Year two, write off	0		0
Year five, write off	0		0
Before five years prior, write off	0		0
Revolving loans, write off	0		0
Revolving loans converted to term loan, write off	0		0
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Pass [Member]
Year one	0		1,127
Year two	1,121		0
Year three	0		2,143
Year four	2,125		2,447
Year five	2,426		524
Before five years prior	5,137		4,676
Revolving loans	252		201
Revolving loans converted to term loan	0		0
Total, gross	11,061		11,118
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Special Mention [Member]
Year one	0
Year two	0
Year three	0
Year four	0
Year five	0
Before five years prior	0
Revolving loans	0
Revolving loans converted to term loan	0
Total, gross	0
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Substandard [Member]
Year one	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		59
Before five years prior	839		765
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	839		824
Residential Portfolio Segment [Member] | Construction Loans [Member] | Substandard [Member]
Year one	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
Before five years prior	0
Revolving loans	0		319
Revolving loans converted to term loan	0		254
Total, gross	0		573
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Year one	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
Before five years prior	0		0
Revolving loans	34,791		35,441
Revolving loans converted to term loan	3,250		3,272
Total, gross	38,041		38,713
Year one, write off	0		0
Year three, write off	0		0
Year four, write off	0		0
Total, gross, write off	0	(0)	0
Year two, write off	0		0
Year five, write off	0		0
Before five years prior, write off	0		0
Revolving loans, write off	0		0
Revolving loans converted to term loan, write off	0		0
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member] | Pass [Member]
Year one	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
Revolving loans	34,452		35,122
Revolving loans converted to term loan	2,943		3,018
Total, gross	37,395		38,140
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member] | Substandard [Member]
Year one	0
Year two	0
Year three	0
Year four	0
Year five	0
Revolving loans	339
Revolving loans converted to term loan	307
Total, gross	646
Commercial and Residential Portfolio Segments [Member]
Year one	31,545		130,255
Year two	137,702		192,327
Year three	193,727		122,844
Year four	117,529		101,379
Year five	99,736		58,396
Before five years prior	222,238		172,293
Revolving loans	77,839		76,074
Revolving loans converted to term loan	3,250		3,272
Total, gross	883,566		856,840
Year one, write off	0		0
Year three, write off	43		40
Year four, write off	0		14
Total, gross, write off	43		123
Year two, write off	0		34
Year five, write off	0		0
Before five years prior, write off	0		10
Revolving loans, write off	0		25
Revolving loans converted to term loan, write off	0		0
Commercial and Residential Portfolio Segments [Member] | Pass [Member]
Year one	30,388		122,177
Year two	131,951		183,092
Year three	185,004		121,081
Year four	113,776		99,542
Year five	97,715		57,185
Before five years prior	213,061		164,784
Revolving loans	76,803		74,941
Revolving loans converted to term loan	2,943		3,018
Total, gross	851,641		825,820
Commercial and Residential Portfolio Segments [Member] | Special Mention [Member]
Year one	1,157		1,852
Year two	1,525		813
Year three	755		399
Year four	390		1,216
Year five	1,423		47
Before five years prior	4,634		4,201
Revolving loans	675		791
Revolving loans converted to term loan	0		0
Total, gross	10,559		9,319
Commercial and Residential Portfolio Segments [Member] | Substandard [Member]
Year one	0		6,226
Year two	4,226		8,422
Year three	7,968		1,364
Year four	3,363		621
Year five	598		1,164
Before five years prior	4,543
Revolving loans	361		342
Revolving loans converted to term loan	307		254
Total, gross	21,366		21,701
Consumer Portfolio Segment [Member]
Year one	876		34,458
Year two	31,848		33,499
Year three	30,864		17,144
Year four	15,600		9,016
Year five	7,972		6,614
Before five years prior	8,428		3,741
Revolving loans	144		159
Revolving loans converted to term loan	0		0
Total, gross	95,732		104,631
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Year one	0		32,047
Year two	29,973		32,141
Year three	29,634		16,425
Year four	14,963		8,764
Year five	7,794		6,557
Before five years prior	8,373		3,726
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	90,737		99,660
Year one, write off	0		0
Year three, write off	264		569
Year four, write off	46		237
Total, gross, write off	633	293	1,550
Year two, write off	127		367
Year five, write off	65		255
Before five years prior, write off	131		122
Revolving loans, write off	0		0
Revolving loans converted to term loan, write off	0		0
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Performing Financial Instruments [Member]
Year one	0		31,880
Year two	29,872		31,913
Year three	29,531		16,246
Year four	14,772		8,554
Year five	7,595		6,329
Before five years prior	8,182		3,689
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	89,952		98,611
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Nonperforming Financial Instruments [Member]
Year one	0		167
Year two	101		228
Year three	103		179
Year four	191		210
Year five	199		228
Before five years prior	191		37
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	785		1,049
Consumer Portfolio Segment [Member] | Other Loans [Member]
Year one	876		2,411
Year two	1,875		1,358
Year three	1,230		719
Year four	637		252
Year five	178		57
Before five years prior	55		15
Revolving loans	144		159
Revolving loans converted to term loan	0		0
Total, gross	4,995		4,971
Year one, write off	0		0
Year three, write off	1		33
Year four, write off	0		9
Total, gross, write off	4	$ 15	129
Year two, write off	2		70
Year five, write off	0		12
Before five years prior, write off	1		3
Revolving loans, write off	0		2
Revolving loans converted to term loan, write off	0		0
Consumer Portfolio Segment [Member] | Other Loans [Member] | Performing Financial Instruments [Member]
Year one	876		2,411
Year two	1,875		1,354
Year three	1,227		719
Year four	637		252
Year five	178		57
Before five years prior	55		15
Revolving loans	144		159
Revolving loans converted to term loan	0		0
Total, gross	4,992		4,967
Consumer Portfolio Segment [Member] | Other Loans [Member] | Nonperforming Financial Instruments [Member]
Year one	0		0
Year two	0		4
Year three	3		0
Year four	0		0
Year five	0		0
Before five years prior	0		0
Revolving loans	0		0
Revolving loans converted to term loan	0		0
Total, gross	$ 3		$ 4