Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 06, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Registrant Name	FIRST MID BANCSHARES, INC.
Entity Central Index Key	0000700565
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		16,736,442
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock
Trading Symbol	FMBH
Security Exchange Name	NASDAQ
Entity File Number	0-13368
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	37-1103704
Entity Address, Address Line One	1421 Charleston Avenue
Entity Address, City or Town	Mattoon
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	61938
City Area Code	217
Local Phone Number	234-7454
Document Quarterly Report	true
Document Transition Report	false