Note 4 - Allowance for Credit Losses - Allowance by Impairment Methodology and Loans by Impairment Methodology (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Balance	$ 16,400	$ 11,974	$ 11,974
Charge-offs	(4,052)	(2,601)	(4,034)
Recoveries	264	185	284
Provision for (recovery of) credit losses on loans	1,835	3,146
Balance	14,447	12,704	16,400
Individually evaluated	1,629	3,377	3,079
Collectively evaluated	12,818	9,327
Loans	1,433,197	994,720	1,466,595
Individually evaluated	5,655	5,993	6,971
Collectively evaluated	1,427,542	988,727	1,459,624
Initial Provision on Non-PCD Touchstone loans	1,835	3,146
Collectively evaluated			13,321
Loans Before Business Acquisitions [Member]
Provision for (recovery of) credit losses on loans			3,961
Initial Provision on Non-PCD Touchstone loans			3,961
Financial Asset Acquired and No Credit Deterioration [Member]
Loans	503,693		603,046
Touchstone Bankshares, Inc [Member]
Initial Allowance on PCD Touchstone loans			386
Touchstone Bankshares, Inc [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Provision for (recovery of) credit losses on loans			3,829
Initial Provision on Non-PCD Touchstone loans			3,829
Real Estate 1 [Member] \| Construction and Land Development [Member]
Balance	585	312	312
Charge-offs	(22)	(4)	(4)
Recoveries	3	0	0
Provision for (recovery of) credit losses on loans	(67)	83
Balance	499	391	585
Individually evaluated	0	0	0
Collectively evaluated	499	391
Loans	78,470	61,446	84,480
Individually evaluated	47	34	50
Collectively evaluated	78,423	61,412	84,430
Initial Provision on Non-PCD Touchstone loans	(67)	83
Collectively evaluated			585
Real Estate 1 [Member] \| Construction and Land Development [Member] \| Loans Before Business Acquisitions [Member]
Provision for (recovery of) credit losses on loans			148
Initial Provision on Non-PCD Touchstone loans			148
Real Estate 1 [Member] \| Construction and Land Development [Member] \| Touchstone Bankshares, Inc [Member]
Initial Allowance on PCD Touchstone loans			11
Real Estate 1 [Member] \| Construction and Land Development [Member] \| Touchstone Bankshares, Inc [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Provision for (recovery of) credit losses on loans			118
Initial Provision on Non-PCD Touchstone loans			118
Real Estate 1 [Member] \| Secured by Multi-family Residential Properties [Member]
Balance	4,266	3,159	3,159
Charge-offs	(44)	(10)	(38)
Recoveries	26	8	22
Provision for (recovery of) credit losses on loans	676	(313)
Balance	4,924	2,844	4,266
Individually evaluated	0	0	0
Collectively evaluated	4,924	2,844
Loans	533,458	351,004	547,167
Individually evaluated	2,060	836	2,148
Collectively evaluated	531,398	350,168	545,019
Initial Provision on Non-PCD Touchstone loans	676	(313)
Collectively evaluated			4,266
Real Estate 1 [Member] \| Secured by Multi-family Residential Properties [Member] \| Loans Before Business Acquisitions [Member]
Provision for (recovery of) credit losses on loans			(360)
Initial Provision on Non-PCD Touchstone loans			(360)
Real Estate 1 [Member] \| Secured by Multi-family Residential Properties [Member] \| Touchstone Bankshares, Inc [Member]
Initial Allowance on PCD Touchstone loans			173
Real Estate 1 [Member] \| Secured by Multi-family Residential Properties [Member] \| Touchstone Bankshares, Inc [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Provision for (recovery of) credit losses on loans			1,310
Initial Provision on Non-PCD Touchstone loans			1,310
Real Estate 1 [Member] \| Other Real Estate Loans [Member]
Balance	7,462	4,698	4,698
Charge-offs	(7)	0	0
Recoveries	12	2	3
Provision for (recovery of) credit losses on loans	(1,577)	422
Balance	5,890	5,122	7,462
Individually evaluated	0	0	0
Collectively evaluated	5,890	5,122
Loans	684,535	449,746	672,162
Individually evaluated	921	0	0
Collectively evaluated	683,614	449,746	672,162
Initial Provision on Non-PCD Touchstone loans	(1,577)	422
Collectively evaluated			7,462
Real Estate 1 [Member] \| Other Real Estate Loans [Member] \| Loans Before Business Acquisitions [Member]
Provision for (recovery of) credit losses on loans			1,190
Initial Provision on Non-PCD Touchstone loans			1,190
Real Estate 1 [Member] \| Other Real Estate Loans [Member] \| Touchstone Bankshares, Inc [Member]
Initial Allowance on PCD Touchstone loans			201
Real Estate 1 [Member] \| Other Real Estate Loans [Member] \| Touchstone Bankshares, Inc [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Provision for (recovery of) credit losses on loans			1,370
Initial Provision on Non-PCD Touchstone loans			1,370
Commercial and Industrial Loans [Member]
Balance	3,927	3,706	3,706
Charge-offs	(3,586)	(2,355)	(3,699)
Recoveries	101	67	111
Provision for (recovery of) credit losses on loans	2,458	2,805
Balance	2,900	4,223	3,927
Individually evaluated	1,629	3,377	3,079
Collectively evaluated	1,271	846
Loans	117,412	114,823	141,333
Individually evaluated	2,627	5,123	4,773
Collectively evaluated	114,785	109,700	136,560
Initial Provision on Non-PCD Touchstone loans	2,458	2,805
Collectively evaluated			848
Commercial and Industrial Loans [Member] \| Loans Before Business Acquisitions [Member]
Provision for (recovery of) credit losses on loans			3,665
Initial Provision on Non-PCD Touchstone loans			3,665
Commercial and Industrial Loans [Member] \| Touchstone Bankshares, Inc [Member]
Initial Allowance on PCD Touchstone loans			1
Commercial and Industrial Loans [Member] \| Touchstone Bankshares, Inc [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Provision for (recovery of) credit losses on loans			143
Initial Provision on Non-PCD Touchstone loans			143
Consumer and Other Loans [Member]
Balance	160	99	99
Charge-offs	(393)	(232)	(293)
Recoveries	122	108	148
Provision for (recovery of) credit losses on loans	345	149
Balance	234	124	160
Individually evaluated	0	0	0
Collectively evaluated	234	124
Loans	19,322	17,701	21,453
Individually evaluated	0	0	0
Collectively evaluated	19,322	17,701	21,453
Initial Provision on Non-PCD Touchstone loans	$ 345	$ 149
Collectively evaluated			160
Consumer and Other Loans [Member] \| Loans Before Business Acquisitions [Member]
Provision for (recovery of) credit losses on loans			(682)
Initial Provision on Non-PCD Touchstone loans			(682)
Consumer and Other Loans [Member] \| Touchstone Bankshares, Inc [Member]
Initial Allowance on PCD Touchstone loans			0
Consumer and Other Loans [Member] \| Touchstone Bankshares, Inc [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Provision for (recovery of) credit losses on loans			888
Initial Provision on Non-PCD Touchstone loans			$ 888

FIRST NATIONAL CORP /VA/ 10-Q