| Document And Entity Information | Apr. 27, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | FIRST COMMUNITY BANKSHARES, INC. |
| Document, Type | 8-K |
| Document, Period End Date | Apr. 27, 2021 |
| Entity, Incorporation, State or Country Code | VA |
| Entity, File Number | 000-19297 |
| Entity, Tax Identification Number | 55-0694814 |
| Entity, Address, Address Line One | P.O. Box 989 |
| Entity, Address, City or Town | Bluefield |
| Entity, Address, State or Province | VA |
| Entity, Address, Postal Zip Code | 24605-0989 |
| City Area Code | 276 |
| Local Phone Number | 326-9000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | FCBC |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000859070 |
