XML 45 R39.htm IDEA: XBRL DOCUMENT
v3.20.1

General (Details) - Estimated - One-time cumulative-effect adjustment $ in Millions | Jan. 01, 2020 USD ($)
--- | ---
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Life of loan portfolio | 4 years
Reserve for potential losses from unfunded commitments | $ 18
Minimum |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Increase in allowance | 55.00%
Maximum |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Increase in allowance | 65.00%

X
- Definition Allowance for Credit Loss, Increase, Percent + References No definition available. + Details
Name: | frme_AllowanceforCreditLossIncreasePercent
Namespace Prefix: | frme_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Loan Portfolio, Term + References No definition available. + Details
Name: | frme_LoanPortfolioTerm
Namespace Prefix: | frme_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118956080&loc=d3e11927-110247 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=118955202&loc=SL82919202-210446 + Details
Name: | us-gaap_OffBalanceSheetCreditLossLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | srt_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | frme_CumulativeEffectPeriodOfAdoptionAxis=frme_CumulativeEffectPeriodOfAdoptionAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |