Regulatory Capital - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) $ in Thousands	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Phantom section (for regulatory ratios):
Capital ($)	$ 935,189	$ 894,259
Capital to RWA (%)	0.1537	0.1484
Capital Required for Capital Adequacy ($)	$ 639,015	$ 632,724
Capital Required for Capital Adequacy to RWA (%)	0.105	0.105
Tier One Risk Based Capital ($)	$ 780,096	$ 724,186
Tier One Risk Based Capital to RWA (%)	0.1282	0.1202
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 517,298	$ 512,205
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.085	0.085
Common Equity Tier One Risk Based Capital ($)	$ 755,816	$ 700,128
Common Equity Tier One Risk Based Capital To RWA (%)	0.1242	0.1162
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 426,010	$ 421,816
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.07	0.07
Tier One Leverage Capital to Average Assets	$ 780,096	$ 724,186
Tier One Leverage Capital to Average Assets (%)	0.1033	0.0933
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 301,976	$ 310,587
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	0.04	0.04
First Mid Bank
Phantom section (for regulatory ratios):
Capital ($)	$ 880,621	$ 854,235
Capital to RWA (%)	0.1451	0.1422
Capital Required for Capital Adequacy ($)	$ 637,089	$ 630,581
Capital Required for Capital Adequacy to RWA (%)	0.105	0.105
Capital Required to be Well Capitalized ($)	$ 606,752	$ 600,553
Capital Required to be Well Capitalized to RWA (%)	0.10	0.10
Tier One Risk Based Capital ($)	$ 813,000	$ 790,917
Tier One Risk Based Capital to RWA (%)	0.134	0.1317
Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer ($)	$ 515,739	$ 510,470
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 ($)	$ 485,401	$ 480,443
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)	0.08	0.08
Common Equity Tier One Risk Based Capital ($)	$ 813,000	$ 790,917
Common Equity Tier One Risk Based Capital To RWA (%)	0.134	0.1317
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 424,726	$ 420,387
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 ($)	$ 394,389	$ 390,360
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	$ 813,000	$ 790,917
Tier One Leverage Capital to Average Assets (%)	0.1082	0.1023
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 300,596	$ 309,151
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	0.04	0.04
Tier One Leverage Capital Required to be Well Capitalized ($)	$ 375,745	$ 386,439
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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