Regulatory Capital (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Phantom section (for regulatory ratios):
Capital ($)	$ 412,879	$ 290,843
Capital to RWA (%)	13.63%	12.70%
Capital Required for Capital Adequacy ($)	$ 299,148	$ 211,848
Capital Required for Capital Adequacy to RWA (%)	9.875%	9.25%
Tier One Risk Based Capital ($)	$ 386,690	$ 270,866
Tier One Risk Based Capital to RWA (%)	12.76%	11.83%
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 238,561	$ 166,043
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	7.875%	7.25%
Common Equity Tier One Risk Based Capital ($)	$ 357,690	$ 246,866
Common Equity Tier One Risk Based Capital To RWA (%)	11.81%	10.78%
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 193,121	$ 131,690
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	6.375%	5.75%
Tier One Leverage Capital to Average Assets (%)	11.15%	9.91%
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 138,765	$ 109,381
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	4.00%	4.00%
Description of Regulatory Requirements, Capital Adequacy Purposes	Quantitative measures established by each regulatory capital standards to ensure capital adequacy require the Company and its subsidiary bank to maintain a minimum capital amounts and ratios (set forth in the table below).
First Clover Leaf [Member]
Phantom section (for regulatory ratios):
Capital ($)	$ 45,387
Capital to RWA (%)	14.33%
Capital Required for Capital Adequacy ($)	$ 31,283
Capital Required for Capital Adequacy to RWA (%)
Capital Required to be Well Capitalized ($)	31,679
Capital Required to be Well Capitalized to RWA (%)
Tier One Risk Based Capital ($)	$ 45,387
Tier One Risk Based Capital to RWA (%)	14.33%
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 24,947
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)
Tier One Risk Based Capital Required to be Well Capitalized ($)	25,343
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)
Common Equity Tier One Risk Based Capital ($)	$ 45,387
Common Equity Tier One Risk Based Capital To RWA (%)	14.33%
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 20,195
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized ($)	$ 20,591
Common Equity Tier One Risk Based Capital Required To Be Well Capitalized to RiWA (%)
Tier One Leverage Capital to Average Assets (%)	11.12%
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 16,322
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)
Tier One Leverage Capital Required to be Well Capitalized ($)	20,403
Tier One Leverage Capital Required to be Well Capitalized to Average Assets (%)
First Mid Bank [Member]
Phantom section (for regulatory ratios):
Capital ($)	$ 350,361	$ 282,621
Capital to RWA (%)	12.85%	12.39%
Capital Required for Capital Adequacy ($)	$ 269,171	$ 211,064
Capital Required for Capital Adequacy to RWA (%)	9.875%	9.25%
Capital Required to be Well Capitalized ($)	$ 272,578	$ 228,177
Capital Required to be Well Capitalized to RWA (%)	10.00%	10.00%
Tier One Risk Based Capital ($)	$ 324,172	$ 262,644
Tier One Risk Based Capital to RWA (%)	11.89%	11.51%
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 214,655	$ 165,428
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	7.875%	7.25%
Tier One Risk Based Capital Required to be Well Capitalized ($)	$ 218,063	$ 182,542
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)	8.00%	8.00%
Common Equity Tier One Risk Based Capital ($)	$ 324,172	$ 262,644
Common Equity Tier One Risk Based Capital To RWA (%)	11.89%	11.51%
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 173,769	$ 131,202
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	6.375%	5.75%
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized ($)	$ 177,176	$ 148,315
Common Equity Tier One Risk Based Capital Required To Be Well Capitalized to RiWA (%)	6.50%	6.50%
Tier One Leverage Capital to Average Assets (%)	9.92%	9.63%
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 130,716	$ 109,113
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized ($)	$ 163,396	$ 136,392
Tier One Leverage Capital Required to be Well Capitalized to Average Assets (%)	5.00%	5.00%

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