Regulatory Capital (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Phantom section (for regulatory ratios):
Capital ($)	$ 290,843	$ 270,062
Capital to RWA (%)	12.70%	12.79%
Capital Required for Capital Adequacy ($)	$ 211,848	$ 182,137
Capital Required for Capital Adequacy to RWA (%)	9.25%	8.63%
Tier One Risk Based Capital ($)	$ 270,866	$ 253,258
Tier One Risk Based Capital to RWA (%)	11.83%	11.99%
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 166,043	$ 139,903
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	7.25%	6.63%
Common Equity Tier One Risk Based Capital ($)	$ 246,866	$ 229,341
Common Equity Tier One Risk Based Capital To RWA (%)	10.78%	10.86%
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 131,690	$ 108,226
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	5.75%	5.13%
Tier One Leverage Capital to Average Assets (%)	9.91%	9.19%
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 109,381	$ 110,242
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 ($)		$ 78,145
Capital to RWA (%)		15.08%
Capital Required for Capital Adequacy ($)		$ 44,698
Capital Required for Capital Adequacy to RWA (%)		8.63%
Capital Required to be Well Capitalized ($)		$ 51,824
Capital Required to be Well Capitalized to RWA (%)		10.00%
Tier One Risk Based Capital ($)		$ 78,145
Tier One Risk Based Capital to RWA (%)		15.08%
Tier One Risk Based Capital Required for Capital Adequacy ($)		$ 34,333
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)		6.63%
Tier One Risk Based Capital Required to be Well Capitalized ($)		$ 41,459
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)		8.00%
Common Equity Tier One Risk Based Capital ($)		$ 78,145
Common Equity Tier One Risk Based Capital To RWA (%)		15.08%
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)		$ 26,560
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)		5.13%
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized ($)		$ 33,685
Common Equity Tier One Risk Based Capital Required To Be Well Capitalized to RiWA (%)		6.50%
Tier One Leverage Capital to Average Assets (%)		12.04%
Tier One Leverage Capital Required for Capital Adequacy ($)		$ 25,963
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)		4.00%
Tier One Leverage Capital Required to be Well Capitalized ($)		$ 32,453
Tier One Leverage Capital Required to be Well Capitalized to Average Assets (%)		5.00%
First Mid Bank [Member]
Phantom section (for regulatory ratios):
Capital ($)	$ 282,621	$ 197,552
Capital to RWA (%)	12.39%	12.44%
Capital Required for Capital Adequacy ($)	$ 211,064	$ 137,019
Capital Required for Capital Adequacy to RWA (%)	9.25%	8.63%
Capital Required to be Well Capitalized ($)	$ 228,177	$ 158,817
Capital Required to be Well Capitalized to RWA (%)	10.00%	10.00%
Tier One Risk Based Capital ($)	$ 262,644	$ 180,826
Tier One Risk Based Capital to RWA (%)	11.51%	11.39%
Tier One Risk Based Capital Required for Capital Adequacy ($)	$ 165,428	$ 105,247
Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	7.25%	6.63%
Tier One Risk Based Capital Required to be Well Capitalized ($)	$ 182,542	$ 127,090
Tier One Risk Based Capital Required to be Well Capitalized to RWA (%)	8.00%	8.00%
Common Equity Tier One Risk Based Capital ($)	$ 262,644	$ 180,826
Common Equity Tier One Risk Based Capital To RWA (%)	11.51%	11.39%
Common Equity Tier One Risk Based Capital Required For Capital Adequacy ($)	$ 131,202	$ 81,417
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to RWA (%)	5.75%	5.13%
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized ($)	$ 148,315	$ 103,261
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 (%)	9.63%	8.62%
Tier One Leverage Capital Required for Capital Adequacy ($)	$ 109,113	$ 83,938
Tier One Leverage Capital Required for Capital Adequacy to Average Assets (%)	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized ($)	$ 136,392	$ 104,922
Tier One Leverage Capital Required to be Well Capitalized to Average Assets (%)	5.00%	5.00%

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