| Document and Entity Information | Jan. 31, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | BAY BANKS OF VIRGINIA INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001034594 |
| Document Type | 8-K |
| Document Period End Date | Jan. 31, 2021 |
| Entity Incorporation State Country Code | VA |
| Entity File Number | 0-22955 |
| Entity Tax Identification Number | 54-1838100 |
| Entity Address, Address Line One | 1801 Bayberry Court |
| Entity Address, City or Town | Richmond |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 23226 |
| City Area Code | (804) |
| Local Phone Number | 404-9668 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
