Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	Apr. 22, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Trading Symbol	FMAO
Entity Registrant Name	FARMERS & MERCHANTS BANCORP, INC.
Entity Central Index Key	0000792966
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		13,065,883
Entity File Number	001-38084
Entity Tax Identification Number	34-1469491
Entity Address, Address Line One	307 North Defiance Street
Entity Address, City or Town	Archbold
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	43502
City Area Code	419
Local Phone Number	446-2501
Entity Incorporation, State or Country Code	OH
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, No Par Value
Security Exchange Name	NASDAQ