Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 06, 2020
Cover [Abstract]
Entity Registrant Name	Fauquier Bankshares, Inc.
Entity Central Index Key	0001083643
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		3,794,725
Document Fiscal Year Focus	2020
Trading Symbol	FBSS
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	000-25805
Entity Tax Identification Number	54-1288193
Entity Address Line One	10 Courthouse Square
Entity Address Town	Warrenton
Entity Address State	VA
Entity Address Postal Zip Code	20186
City Area Code	540
Local Phone Number	347-2700
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common StockPar value $3.13 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	VA
Document Quarterly Report	true
Document Transition Report	false