Regulatory Capital - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) $ in Thousands	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Banking Regulation, Risk-Based Information [Abstract]
Capital ($)	$ 968,670	$ 935,189
Capital to RWA (%)	0.1576	0.1537
Capital Required for Capital Adequacy ($)	$ 645,528	$ 639,015
Capital Required for Capital Adequacy to RWA (%)	0.105	0.105
Tier One Risk Based Capital ($)	$ 818,499	$ 780,096
Tier One Risk Based Capital to RWA (%)	0.1331	0.1282
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 522,570	$ 517,298
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.085	0.085
Common Equity Tier One Risk Based Capital ($)	$ 794,115	$ 755,816
Common Equity Tier One Risk Based Capital To RWA (%)	0.1292	0.1242
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 430,352	$ 426,010
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.07	0.07
Tier One Leverage Capital to Average Assets	$ 818,499	$ 780,096
Tier One Leverage Capital to Average Assets (%)	0.1073	0.1033
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 305,223	$ 301,976
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	0.04	0.04
First Mid Bank
Banking Regulation, Risk-Based Information [Abstract]
Capital ($)	$ 894,817	$ 880,621
Capital to RWA (%)	0.1461	0.1451
Capital Required for Capital Adequacy ($)	$ 643,182	$ 637,089
Capital Required for Capital Adequacy to RWA (%)	0.105	0.105
Capital Required to be Well Capitalized ($)	$ 612,554	$ 606,752
Capital Required to be Well Capitalized to RWA (%)	0.10	0.10
Tier One Risk Based Capital ($)	$ 824,236	$ 813,000
Tier One Risk Based Capital to RWA (%)	0.1346	0.134
Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer ($)	$ 520,671	$ 515,739
Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer to RWA (%)	0.085	0.085
Tier One Risk Based Capital Required to be Well Capitalized ($)	$ 490,043	$ 485,401
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)	0.08	0.08
Common Equity Tier One Risk Based Capital ($)	$ 824,236	$ 813,000
Common Equity Tier One Risk Based Capital To RWA (%)	0.1346	0.134
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 428,788	$ 424,726
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.07	0.07
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized ($)	$ 398,160	$ 394,389
Common Equity Tier One Risk Based Capital Required To Be Well Capitalized to RiWA (%)	0.065	0.065
Tier One Leverage Capital to Average Assets	$ 824,236	$ 813,000
Tier One Leverage Capital to Average Assets (%)	0.1085	0.1082
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 303,954	$ 300,596
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	0.04	0.04
Tier One Leverage Capital Required to be Well Capitalized ($)	$ 379,943	$ 375,745
Tier One Leverage Capital Required to be Well Capitalized to Average Assets (%)	0.05	0.05

Tier one risk based capital required for capital adequacy with buffer.

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Tier one risk based capital required for capital adequacy with buffer to risk weighted assets.

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Ratio of minimum Common Equity Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

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Amount of total capital as defined by regulatory framework.

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