Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting and Consolidation	Basis of Accounting and Consolidation The accompanying consolidated financial statements include the accounts of First Mid-Illinois Bancshares, Inc. (“Company”) and its wholly-owned subsidiaries: Mid-Illinois Data Services, Inc. (“MIDS”), First Mid Wealth Management, First Mid Bank & Trust, N.A. (“First Mid Bank”), Soy Capital Bank and Trust Company ("Soy Capital Bank"), and First Mid Insurance Group (“First Mid Insurance”). All significant intercompany balances and transactions have been eliminated in consolidation. Certain amounts in the prior year’s consolidated financial statements have been reclassified to conform to the 2018 presentation and there was no impact on net income or stockholders’ equity from these reclassifications. The Company operates as a single segment entity for financial reporting purposes. The accounting and reporting policies of the Company conform to accounting principles generally accepted in the United States of America. Following is a description of the more significant of these policies.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The Company uses estimates and employs the judgments of management in determining the amount of its allowance for loan losses and income tax accruals and deferrals, in its fair value measurements of investment securities, and in the evaluation of impairment of loans, goodwill, investment securities, and premises and equipment. As with any estimate, actual results could differ from these estimates. Material estimates that are particularly susceptible to significant change relate to the determination of the allowance for loan losses. In connection with the determination of the allowance for loan losses, management obtains independent appraisals for significant properties.
Fair Value Measurements	Fair Value Measurements The fair value of a financial instrument is defined as the amount at which the instrument could be exchanged in a current transaction between willing parties, other than in a forced or liquidation sale. The Company estimates the fair value of a financial instrument using a variety of valuation methods. Where financial instruments are actively traded and have quoted market prices, quoted market prices are used for fair value. When the financial instruments are not actively traded, other observable market inputs, such as quoted prices of securities with similar characteristics, may be used, if available, to determine fair value. When observable market prices do not exist, the Company estimates fair value. The Company’s valuation methods consider factors such as liquidity and concentration concerns. Other factors such as model assumptions, market dislocations, and unexpected correlations can affect estimates of fair value. Imprecision in estimating these factors can impact the amount of revenue or loss recorded. At the end of each quarter, the Company assesses the valuation hierarchy for each asset or liability measured. From time to time, assets or liabilities may be transferred within hierarchy levels due to changes in availability of observable market inputs to measure fair value at the measurement date. Transfers into or out of hierarchy levels are based upon the fair value at the beginning of the reporting period. A more detailed description of the fair values measured at each level of the fair value hierarchy can be found in Note 11 – “Disclosures of Fair Values of Financial Instruments.”
Cash and Cash Equivalents and Certificates of Deposit Investments	Cash and Cash Equivalents For purposes of reporting cash flows, cash equivalents include non-interest bearing and interest bearing cash and due from banks and federal funds sold. Generally, federal funds are sold for one-day periods. Certificates of Deposit Investments Certificates of deposit investments have original maturities of three to five years and are carried at cost.
Investment Securities	Investment Securities The Company classifies its investments in debt securities as either held-to-maturity or available-for-sale in accordance with ASC 320. Securities classified as held-to-maturity are recorded at cost or amortized cost. Available-for-sale securities are carried at fair value. Fair value calculations are based on quoted market prices when such prices are available. If quoted market prices are not available, estimates of fair value are computed using a variety of techniques, including extrapolation from the quoted prices of similar instruments or recent trades for thinly traded securities, fundamental analysis, or through obtaining purchase quotes. Due to the subjective nature of the valuation process, it is possible that the actual fair values of these investments could differ from the estimated amounts, thereby affecting the financial position, results of operations and cash flows of the Company. If the estimated value of investments is less than the cost or amortized cost, the Company evaluates whether an event or change in circumstances has occurred that may have a significant adverse effect on the fair value of the investment. If such an event or change has occurred and the Company determines that the impairment is other-than-temporary, a further determination is made as to the portion of impairment that is related to credit loss. The impairment of the investment that is related to the credit loss is expensed in the period in which the event or change occurred. The remainder of the impairment is recorded in other comprehensive income.
Loans	Loans Loans are stated at the principal amount outstanding net of unearned discounts, unearned income and the allowance for loan losses. Unearned income includes deferred loan origination fees reduced by loan origination costs and is amortized to interest income over the life of the related loan using methods that approximate the effective interest rate method. Interest on substantially all loans is credited to income based on the principal amount outstanding. The Company’s policy is to discontinue the accrual of interest income on any loan that becomes ninety days past due as to principal or interest or earlier when, in the opinion of management there is reasonable doubt as to the timely collection of principal or interest. Nonaccrual loans are returned to accrual status when, in the opinion of management, the financial position of the borrower indicates there is no longer any reasonable doubt as to the timely collectability of interest or principal. Loans expected to be sold are classified as held for sale in the consolidated financial statements and are recorded at the lower of aggregate cost or market value, taking into consideration future commitments to sell the loans.
Allowance for Loan Losses	Allowance for Loan Losses The Company believes the allowance for loan losses is the critical accounting policy that requires the most significant judgments and assumptions used in the preparation of its consolidated financial statements. An estimate of potential losses inherent in the loan portfolio is determined and an allowance for those losses is established by considering factors including historical loss rates, expected cash flows and estimated collateral values. In assessing these factors, the Company uses organizational history and experience with credit decisions and related outcomes. The allowance for loan losses represents the best estimate of losses inherent in the existing loan portfolio. The allowance for loan losses is increased by the provision for loan losses charged to expense and reduced by loans charged off, net of recoveries. The Company evaluates the allowance for loan losses quarterly. If the underlying assumptions later prove to be inaccurate based on subsequent loss evaluations, the allowance for loan losses is adjusted. The Company estimates the appropriate level of allowance for loan losses by separately evaluating impaired and nonimpaired loans. A specific allowance is assigned to an impaired loan when expected cash flows or collateral do not justify the carrying amount of the loan. The methodology used to assign an allowance to a nonimpaired loan is more subjective. Generally, the allowance assigned to nonimpaired loans is determined by applying historical loss rates to existing loans with similar risk characteristics, adjusted for qualitative factors including the volume and severity of identified classified loans, changes in economic conditions, changes in credit policies or underwriting standards, and changes in the level of credit risk associated with specific industries and markets. Because the economic and business climate in any given industry or market, and its impact on any given borrower, can change rapidly, the risk profile of the loan portfolio is continually assessed and adjusted when appropriate. Notwithstanding these procedures, there still exists the possibility that the assessment could prove to be significantly incorrect and that an immediate adjustment to the allowance for loan losses would be required.
Premises and Equipment	Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is charged to expense and determined principally by the straight-line method over the estimated useful lives of the assets. The estimated useful lives for each major depreciable classification of premises and equipment are as follows:
Goodwill and Intangible Assets	Goodwill and Intangible Assets The Company has goodwill from business combinations, identifiable intangible assets assigned to core deposit relationships and customer lists acquired, and intangible assets arising from the rights to service mortgage loans for others. Identifiable intangible assets generally arise from branches acquired that the Company accounted for as purchases. Such assets consist of the excess of the purchase price over the fair value of net assets acquired, with specific amounts assigned to core deposit relationships and customer lists primarily related to insurance agency. Intangible assets are amortized by the straight-line method over various periods up to fifteen years. Management reviews intangible assets for possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. In accordance with the provisions of SFAS No. 142, “Goodwill and Other Intangible Assets,” codified into ASC 350, the Company performed testing of goodwill for impairment as of September 30, 2018 and determined that, as of that date, goodwill was not impaired. Management also concluded that the remaining amounts and amortization periods were appropriate for all intangible assets.
Other Real Estate Owned	Other Real Estate Owned Other real estate owned acquired through loan foreclosure is initially recorded at fair value less costs to sell when acquired, establishing a new cost basis. The adjustment at the time of foreclosure is recorded through the allowance for loan losses. Due to the subjective nature of establishing the fair value when the asset is acquired, the actual fair value of the other real estate owned or foreclosed asset could differ from the original estimate. If it is determined that fair value temporarily declines subsequent to foreclosure, a valuation allowance is recorded through noninterest expense. Operating costs associated with the assets after acquisition are also recorded as noninterest expense. Gains and losses on the disposition of other real estate owned and foreclosed assets are netted and posted to other noninterest expense.
Federal Home Loan Bank Stock	Federal Home Loan Bank Stock Federal Home Loan Bank stock is a required investment for institutions that are members of the Federal Home Loan Bank system. The required investment in the common stock is based on a predetermined formula.
Income Taxes	Income Taxes The Company and its subsidiaries file consolidated federal and state income tax returns with each organization computing its taxes on a separate company basis. Amounts provided for income tax expense are based on income reported for financial statement purposes rather than amounts currently payable under tax laws. Deferred tax assets and liabilities are recognized for future tax consequences attributable to the temporary differences existing between the financial statement carrying amounts of assets and liabilities and their respective tax basis, as well as operating loss and tax credit carry forwards. To the extent that current available evidence about the future raises doubt about the realization of a deferred tax asset, a valuation allowance is established. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as an increase or decrease in income tax expense in the period in which such change is enacted. On December 22, 2017, the United States enacted certain tax reforms through the Tax Cuts and Jobs Act, which changes existing tax laws, most significantly a change in the statutory corporate tax rate from 35% to 21%. As a result of this enactment, the Company incurred additional one-time income tax expense of approximately $1.4 million during the fourth quarter of 2017, primarily due to remeasurement of deferred tax assets and liabilities. Additionally, the Company reviews its uncertain tax positions annually under FASB Interpretation No. 48 (FIN No. 48), “Accounting for Uncertainty in Income Taxes,” codified within ASC 740. An uncertain tax position is recognized as a benefit only if it is "more likely than not" that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount actually recognized is the largest amount of tax benefit that is greater than 50% likely to be recognized on examination. For tax positions not meeting the "more likely than not" test, no tax benefit is recorded. A significant amount of judgment is applied to determine both whether the tax position meets the "more likely than not" test as well as to determine the largest amount of tax benefit that is greater than 50% likely to be recognized. Differences between the position taken by management and that of taxing authorities could result in a reduction of a tax benefit or increase to tax liability, which could adversely affect future income tax expense.
Trust Department Assets	Trust Department Assets Assets held in fiduciary or agency capacities are not included in the consolidated balance sheets since such items are not assets of the Company or its subsidiaries. Fees from trust activities are recorded on a cash basis over the period in which the service is provided. Fees are a function of the market value of assets managed and administered, the volume of transactions, and fees for other services rendered, as set forth in the underlying client agreement with the Trust & Wealth Management Division of First Mid Bank. This revenue recognition involves the use of estimates and assumptions, including components that are calculated based on asset valuations and transaction volumes. Any out of pocket expenses or services not typically covered by the fee schedule for trust activities are charged directly to the trust account on a gross basis as trust revenue is incurred.
Treasury Stock	Treasury Stock
Stock Incentive Awards	Stock Incentive Awards At the Annual Meeting of Stockholders held April 26, 2017, the stockholders approved the 2017 Stock Incentive Plan ("SI Plan"). The SI Plan was implemented to succeed the Company's 2007 Stock Incentive Plan, which had a ten-year term. The SI Plan is intended to provide a means whereby directors, employees, consultants and advisors of the Company and its Subsidiaries may sustain a sense of proprietorship and personal involvement in the continued development and financial success of the Company and its Subsidiaries, thereby advancing the interests of the Company and its stockholders. Accordingly, directors and selected employees, consultants and advisors may be provided the opportunity to acquire shares of Common Stock of the Company on the terms and conditions established in the SI Plan. A maximum of 149,983 shares of common stock may be issued under the SI Plan. The Company awarded 28,700, 18,391, and 13,912

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The accompanying consolidated financial statements include the accounts of First Mid-Illinois Bancshares, Inc. (“Company”) and its wholly-owned subsidiaries: Mid-Illinois Data Services, Inc. (“MIDS”), First Mid Wealth Management, First Mid Bank & Trust, N.A. (“First Mid Bank”), Soy Capital Bank and Trust Company ("Soy Capital Bank"), and First Mid Insurance Group (“First Mid Insurance”). All significant intercompany balances and transactions have been eliminated in consolidation. Certain amounts in the prior year’s consolidated financial statements have been reclassified to conform to the 2018 presentation and there was no impact on net income or stockholders’ equity from these reclassifications. The Company operates as a single segment entity for financial reporting purposes. The accounting and reporting policies of the Company conform to accounting principles generally accepted in the United States of America. Following is a description of the more significant of these policies.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The Company uses estimates and employs the judgments of management in determining the amount of its allowance for loan losses and income tax accruals and deferrals, in its fair value measurements of investment securities, and in the evaluation of impairment of loans, goodwill, investment securities, and premises and equipment. As with any estimate, actual results could differ from these estimates. Material estimates that are particularly susceptible to significant change relate to the determination of the allowance for loan losses. In connection with the determination of the allowance for loan losses, management obtains independent appraisals for significant properties.

Fair Value Measurements

The fair value of a financial instrument is defined as the amount at which the instrument could be exchanged in a current transaction between willing parties, other than in a forced or liquidation sale. The Company estimates the fair value of a financial instrument using a variety of valuation methods. Where financial instruments are actively traded and have quoted market prices, quoted market prices are used for fair value. When the financial instruments are not actively traded, other observable market inputs, such as quoted prices of securities with similar characteristics, may be used, if available, to determine fair value. When observable market prices do not exist, the Company estimates fair value. The Company’s valuation methods consider factors such as liquidity and concentration concerns. Other factors such as model assumptions, market dislocations, and unexpected correlations can affect estimates of fair value. Imprecision in estimating these factors can impact the amount of revenue or loss recorded.

At the end of each quarter, the Company assesses the valuation hierarchy for each asset or liability measured. From time to time, assets or liabilities may be transferred within hierarchy levels due to changes in availability of observable market inputs to measure fair value at the measurement date. Transfers into or out of hierarchy levels are based upon the fair value at the beginning of the reporting period. A more detailed description of the fair values measured at each level of the fair value hierarchy can be found in Note 11 – “Disclosures of Fair Values of Financial Instruments.”

Cash and Cash Equivalents and Certificates of Deposit Investments

Cash and Cash Equivalents

For purposes of reporting cash flows, cash equivalents include non-interest bearing and interest bearing cash and due from banks and federal funds sold. Generally, federal funds are sold for one-day periods.

Certificates of Deposit Investments

Certificates of deposit investments have original maturities of three to five years and are carried at cost.

Investment Securities

The Company classifies its investments in debt securities as either held-to-maturity or available-for-sale in accordance with ASC 320. Securities classified as held-to-maturity are recorded at cost or amortized cost. Available-for-sale securities are carried at fair value. Fair value calculations are based on quoted market prices when such prices are available. If quoted market prices are not available, estimates of fair value are computed using a variety of techniques, including extrapolation from the quoted prices of similar instruments or recent trades for thinly traded securities, fundamental analysis, or through obtaining purchase quotes. Due to the subjective nature of the valuation process, it is possible that the actual fair values of these investments could differ from the estimated amounts, thereby affecting the financial position, results of operations and cash flows of the Company. If the estimated value of investments is less than the cost or amortized cost, the Company evaluates whether an event or change in circumstances has occurred that may have a significant adverse effect on the fair value of the investment. If such an event or change has occurred and the Company determines that the impairment is other-than-temporary, a further determination is made as to the portion of impairment that is related to credit loss. The impairment of the investment that is related to the credit loss is expensed in the period in which the event or change occurred. The remainder of the impairment is recorded in other comprehensive income.

Loans

Loans are stated at the principal amount outstanding net of unearned discounts, unearned income and the allowance for loan losses. Unearned income includes deferred loan origination fees reduced by loan origination costs and is amortized to interest income over the life of the related loan using methods that approximate the effective interest rate method. Interest on substantially all loans is credited to income based on the principal amount outstanding.

The Company’s policy is to discontinue the accrual of interest income on any loan that becomes ninety days past due as to principal or interest or earlier when, in the opinion of management there is reasonable doubt as to the timely collection of principal or interest. Nonaccrual loans are returned to accrual status when, in the opinion of management, the financial position of the borrower indicates there is no longer any reasonable doubt as to the timely collectability of interest or principal.

Loans expected to be sold are classified as held for sale in the consolidated financial statements and are recorded at the lower of aggregate cost or market value, taking into consideration future commitments to sell the loans.

Allowance for Loan Losses

The Company believes the allowance for loan losses is the critical accounting policy that requires the most significant judgments and assumptions used in the preparation of its consolidated financial statements. An estimate of potential losses inherent in the loan portfolio is determined and an allowance for those losses is established by considering factors including historical loss rates, expected cash flows and estimated collateral values. In assessing these factors, the Company uses organizational history and experience with credit decisions and related outcomes. The allowance for loan losses represents the best estimate of losses inherent in the existing loan portfolio. The allowance for loan losses is increased by the provision for loan losses charged to expense and reduced by loans charged off, net of recoveries. The Company evaluates the allowance for loan losses quarterly. If the underlying assumptions later prove to be inaccurate based on subsequent loss evaluations, the allowance for loan losses is adjusted.

The Company estimates the appropriate level of allowance for loan losses by separately evaluating impaired and nonimpaired loans. A specific allowance is assigned to an impaired loan when expected cash flows or collateral do not justify the carrying amount of the loan. The methodology used to assign an allowance to a nonimpaired loan is more subjective. Generally, the allowance assigned to nonimpaired loans is determined by applying historical loss rates to existing loans with similar risk characteristics, adjusted for qualitative factors including the volume and severity of identified classified loans, changes in economic conditions, changes in credit policies or underwriting standards, and changes in the level of credit risk associated with specific industries and markets. Because the economic and business climate in any given industry or market, and its impact on any given borrower, can change rapidly, the risk profile of the loan portfolio is continually assessed and adjusted when appropriate. Notwithstanding these procedures, there still exists the possibility that the assessment could prove to be significantly incorrect and that an immediate adjustment to the allowance for loan losses would be required.

Premises and Equipment

Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is charged to expense and determined principally by the straight-line method over the estimated useful lives of the assets. The estimated useful lives for each major depreciable classification of premises and equipment are as follows:

Goodwill and Intangible Assets

The Company has goodwill from business combinations, identifiable intangible assets assigned to core deposit relationships and customer lists acquired, and intangible assets arising from the rights to service mortgage loans for others.

Identifiable intangible assets generally arise from branches acquired that the Company accounted for as purchases. Such assets consist of the excess of the purchase price over the fair value of net assets acquired, with specific amounts assigned to core deposit relationships and customer lists primarily related to insurance agency. Intangible assets are amortized by the straight-line method over various periods up to fifteen years. Management reviews intangible assets for possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.

In accordance with the provisions of SFAS No. 142, “Goodwill and Other Intangible Assets,” codified into ASC 350, the Company performed testing of goodwill for impairment as of September 30, 2018 and determined that, as of that date, goodwill was not impaired. Management also concluded that the remaining amounts and amortization periods were appropriate for all intangible assets.

Other Real Estate Owned

Other real estate owned acquired through loan foreclosure is initially recorded at fair value less costs to sell when acquired, establishing a new cost basis. The adjustment at the time of foreclosure is recorded through the allowance for loan losses. Due to the subjective nature of establishing the fair value when the asset is acquired, the actual fair value of the other real estate owned or foreclosed asset could differ from the original estimate. If it is determined that fair value temporarily declines subsequent to foreclosure, a valuation allowance is recorded through noninterest expense. Operating costs associated with the assets after acquisition are also recorded as noninterest expense. Gains and losses on the disposition of other real estate owned and foreclosed assets are netted and posted to other noninterest expense.

Federal Home Loan Bank Stock

Federal Home Loan Bank stock is a required investment for institutions that are members of the Federal Home Loan Bank system. The required investment in the common stock is based on a predetermined formula.

Income Taxes

The Company and its subsidiaries file consolidated federal and state income tax returns with each organization computing its taxes on a separate company basis. Amounts provided for income tax expense are based on income reported for financial statement purposes rather than amounts currently payable under tax laws.

Deferred tax assets and liabilities are recognized for future tax consequences attributable to the temporary differences existing between the financial statement carrying amounts of assets and liabilities and their respective tax basis, as well as operating loss and tax credit carry forwards. To the extent that current available evidence about the future raises doubt about the realization of a deferred tax asset, a valuation allowance is established. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized as an increase or decrease in income tax expense in the period in which such change is enacted.

On December 22, 2017, the United States enacted certain tax reforms through the Tax Cuts and Jobs Act, which changes existing tax laws, most significantly a change in the statutory corporate tax rate from 35% to 21%. As a result of this enactment, the Company incurred additional one-time income tax expense of approximately $1.4 million during the fourth quarter of 2017, primarily due to remeasurement of deferred tax assets and liabilities.

Additionally, the Company reviews its uncertain tax positions annually under FASB Interpretation No. 48 (FIN No. 48), “Accounting for Uncertainty in Income Taxes,” codified within ASC 740. An uncertain tax position is recognized as a benefit only if it is "more likely than not" that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount actually recognized is the largest amount of tax benefit that is greater than 50% likely to be recognized on examination. For tax positions not meeting the "more likely than not" test, no tax benefit is recorded. A significant amount of judgment is applied to determine both whether the tax position meets the "more likely than not" test as well as to determine the largest amount of tax benefit that is greater than 50% likely to be recognized. Differences between the position taken by management and that of taxing authorities could result in a reduction of a tax benefit or increase to tax liability, which could adversely affect future income tax expense.

Trust Department Assets

Assets held in fiduciary or agency capacities are not included in the consolidated balance sheets since such items are not assets of the Company or its subsidiaries. Fees from trust activities are recorded on a cash basis over the period in which the service is provided. Fees are a function of the market value of assets managed and administered, the volume of transactions, and fees for other services rendered, as set forth in the underlying client agreement with the Trust & Wealth Management Division of First Mid Bank. This revenue recognition involves the use of estimates and assumptions, including components that are calculated based on asset valuations and transaction volumes. Any out of pocket expenses or services not typically covered by the fee schedule for trust activities are charged directly to the trust account on a gross basis as trust revenue is incurred.

Treasury Stock

Stock Incentive Awards

At the Annual Meeting of Stockholders held April 26, 2017, the stockholders approved the 2017 Stock Incentive Plan ("SI Plan"). The SI Plan was implemented to succeed the Company's 2007 Stock Incentive Plan, which had a ten-year term. The SI Plan is intended to provide a means whereby directors, employees, consultants and advisors of the Company and its Subsidiaries may sustain a sense of proprietorship and personal involvement in the continued development and financial success of the Company and its Subsidiaries, thereby advancing the interests of the Company and its stockholders. Accordingly, directors and selected employees, consultants and advisors may be provided the opportunity to acquire shares of Common Stock of the Company on the terms and conditions established in the SI Plan.

A maximum of 149,983 shares of common stock may be issued under the SI Plan. The Company awarded 28,700, 18,391, and 13,912