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Employee Benefit Plans (Bank Owned Life Insurance) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Bank owned life insurance [Line Items] |  |
Bank-owned life insurance | $ 52,188 | $ 42,761
Bank owned life insurance death benefits | 136,100 | 97,900
Insured executive officers with deferred compensation plans |  |
Bank owned life insurance [Line Items] |  |
Bank-owned life insurance | 2,700 | 2,600
Bank owned life insurance death benefits | 6,000 | 6,000
Other insured individuals |  |
Bank owned life insurance [Line Items] |  |
Bank-owned life insurance | $ 49,500 | $ 40,200

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- Definition Bank Owned Life Insurance Death Benefits + References No definition available. + Details
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Namespace Prefix: | fbiz_
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Balance Type: | debit
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- Definition [Line Items] for Bank owned life insurance [Table] + References No definition available. + Details
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Data Type: | xbrli:stringItemType
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- Definition The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(10)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
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Balance Type: | debit
Period Type: | instant

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- Details
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- Details
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Data Type: | na
Balance Type: |
Period Type: |