XML 106 R92.htm IDEA: XBRL DOCUMENT
v3.20.4

Other Assets (Trust II) (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019 | Sep. 26, 2008
--- | --- | --- | ---
Variable Interest Entity |  |  |
Sole ownership of common securities issued by Trust II | $ 315,000 |  |
Junior subordinated notes | 10,062,000 | $ 10,047,000 |
Investment in Trust II | $ 315,000 | $ 315,000 |
Trust II |  |  |
Variable Interest Entity |  |  |
Sole ownership of common securities issued by Trust II |  |  | $ 315,000
Junior subordinated notes |  |  | $ 10,000,000.0
Fixed rate |  |  | 10.50%

X
- Definition Investment in Trust II + References No definition available. + Details
Name: | fbiz_InvestmentinTrustII
Namespace Prefix: | fbiz_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Sole ownership of common securities issued by Trust II + References No definition available. + Details
Name: | fbiz_SoleOwnershipOfCommonSecuritiesIssuedByTrustIi
Namespace Prefix: | fbiz_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Trust preferred securities + References No definition available. + Details
Name: | fbiz_TrustPreferredSecurities
Namespace Prefix: | fbiz_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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_VariableInterestEntityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=fbiz_TrustIiMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |