Regulatory Capital - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Phantom section (for regulatory ratios):
Capital ($)	$ 894,259	$ 801,966
Capital to RWA (%)	0.1484	0.152
Capital Required for Capital Adequacy ($)	$ 632,724	$ 554,164
Capital Required for Capital Adequacy to RWA (%)	0.105	0.105
Tier One Risk Based Capital ($)	$ 724,186	$ 654,453
Tier One Risk Based Capital to RWA (%)	0.1202	0.124
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 512,205	$ 448,609
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.085	0.085
Common Equity Tier One Risk Based Capital ($)	$ 700,128	$ 635,089
Common Equity Tier One Risk Based Capital To RWA (%)	0.1162	0.1203
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 421,816	$ 369,442
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	0.07	0.07
Tier One Leverage Capital to Average Assets	$ 724,186	$ 654,453
Tier One Leverage Capital to Average Assets (%)	0.0933	0.0968
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 310,587	$ 268,875
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	0.04	0.04
First Mid Bank
Phantom section (for regulatory ratios):
Capital ($)	$ 854,235	$ 745,624
Capital to RWA (%)	0.1422	0.1418
Capital Required for Capital Adequacy ($)	$ 630,581	$ 552,161
Capital Required for Capital Adequacy to RWA (%)	0.105	0.105
Capital Required to be Well Capitalized ($)	$ 600,553	$ 525,868
Capital Required to be Well Capitalized to RWA (%)	0.10	0.10
Tier One Risk Based Capital ($)	$ 790,917	$ 692,664
Tier One Risk Based Capital to RWA (%)	0.1317	0.1317
Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer ($)	$ 510,470	$ 446,987
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 ($)	$ 480,443	$ 420,694
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)	0.08	0.08
Common Equity Tier One Risk Based Capital ($)	$ 790,917	$ 692,664
Common Equity Tier One Risk Based Capital To RWA (%)	0.1317	0.1317
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 420,387	$ 368,107
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 ($)	$ 390,360	$ 341,814
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	$ 790,917	$ 692,664
Tier One Leverage Capital to Average Assets (%)	0.1023	0.1022
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 309,151	$ 270,990
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	0.04	0.04
Tier One Leverage Capital Required to be Well Capitalized ($)	$ 386,439	$ 338,738
Tier One Leverage Capital Required to be Well Capitalized to Average Assets (%)	0.05	0.05