XML 105 R91.htm IDEA: XBRL DOCUMENT
v3.20.4

Other Assets Other Assets (Investments in Limited Partnerships) (Details) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2020 | Dec. 31, 2019
Schedule of Equity Method Investments |  |  |
Investment in limited partnerships | $ 6,673,000 | $ 6,673,000 | $ 4,476,000
Income from Equity Method Investments | 1,400,000 | 520,000 |
Loss on Equity Method Investments | 121,000 | 99,000 |
Aldine Capital Fund, LP |  |  |
Schedule of Equity Method Investments |  |  |
Investment in limited partnerships | 60,000 | 60,000 | 54,000
Aldine Capital Fund II, LP |  |  |
Schedule of Equity Method Investments |  |  |
Investment in limited partnerships | 3,500,000 | 3,500,000 | 3,100,000
Aldine Capital Fund III, LP |  |  |
Schedule of Equity Method Investments |  |  |
Investment in limited partnerships | 2,800,000 | 2,800,000 | $ 1,300,000
Dane Workforce Housing Fund LLC |  |  |
Schedule of Equity Method Investments |  |  |
Investment in limited partnerships | $ 275,000 | $ 275,000 |

X
- Definition Income from Equity Method Investments + References No definition available. + Details
Name: | fbiz_IncomefromEquityMethodInvestments
Namespace Prefix: | fbiz_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Loss on Equity Method Investments + References No definition available. + Details
Name: | fbiz_LossonEquityMethodInvestments
Namespace Prefix: | fbiz_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=fbiz_AldineCapitalFundLPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=fbiz_AldineCapitalFundIILPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=fbiz_AldineCapitalFundIIILPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=fbiz_DaneWorkforceHousingFundLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |