$FBIZ
FIRST BUSINESS FINANCIAL SERVICES, INC. Stock $fbiz

$fbiz Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000152195121000028 Filed on February 24, 2021

Income Statement

Concept	2019 Q4	2019 Q3	2019 Q2
Revenue	$25.61M	$25.44M	$25.31M
YoY Change	4.45%	7.96%	12.64%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$800.0K	$810.0K	$790.0K
YoY Change	110.53%	118.92%	113.51%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$7.139M	$8.662M	$8.457M
YoY Change	-3.62%	33.9%	52.74%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$7.418M	$6.503M	$5.977M
YoY Change	192.51%	-3.87%	54.56%
Income Tax	$1.650M	$1.418M	-$595.0K
% Of Pretax Income	22.24%	21.81%	-9.95%
Net Earnings	$5.768M	$5.085M	$6.572M
YoY Change	41.93%	-4.07%	99.82%
Net Earnings / Revenue	22.52%	19.99%	25.97%
Basic Earnings Per Share	$0.67	$0.59	$0.75
Diluted Earnings Per Share	$0.67	$0.59	$0.75
COMMON SHARES
Basic Shares Outstanding	8.589M shares	8.492M shares	8.570M shares
Diluted Shares Outstanding		8.492M shares	8.570M shares

Balance Sheet

Concept	2019 Q4	2019 Q3	2019 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$67.10M	$60.96M	$45.88M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$2.557M	$2.740M	$2.866M
YoY Change	-22.14%	-15.61%	-14.65%
Goodwill	$10.70M
YoY Change	0.0%
Intangibles
YoY Change
Long-Term Investments	$12.30M	$13.00M	$2.000M
YoY Change	623.53%	622.22%	11.11%
Other Assets	$5.400M	$2.000M	$3.100M
YoY Change	68.75%	-9.09%	34.78%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$2.097B	$2.093B	$2.070B
YoY Change	6.63%	10.48%	8.98%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$16.90M	$19.30M	$19.20M
YoY Change	0.6%	26.97%	57.38%
Accrued Expenses	$7.500M	$7.900M	$8.200M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$24.40M	$27.20M	$27.40M
YoY Change	45.24%	78.95%	124.59%
LONG-TERM LIABILITIES
Long-Term Debt	$34.40M	$34.40M	$34.50M
YoY Change	-0.29%	-0.29%	0.29%
Other Long-Term Liabilities	$18.30M	$23.10M	$16.40M
YoY Change	297.83%	1825.0%	2242.86%
Total Long-Term Liabilities	$52.70M	$57.50M	$50.90M
YoY Change	34.78%	61.06%	45.01%
TOTAL LIABILITIES
Total Short-Term Liabilities	$24.40M	$27.20M	$27.40M
Total Long-Term Liabilities	$52.70M	$57.50M	$50.90M
Total Liabilities	$1.903B	$1.902B	$1.881B
YoY Change	6.54%	10.79%	9.0%
SHAREHOLDERS EQUITY
Retained Earnings	$129.1M	$124.6M	$120.8M
YoY Change	17.04%	15.98%	16.88%
Common Stock	$81.28M	$80.83M	$80.44M
YoY Change	1.96%	1.73%	1.55%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$14.88M	$13.01M	$11.34M
YoY Change	94.96%	76.38%	59.5%
Treasury Stock Shares	596.7K shares	520.9K shares	450.6K shares
Shareholders Equity	$194.2M	$190.8M	$188.9M
YoY Change
Total Liabilities & Shareholders Equity	$2.097B	$2.093B	$2.070B
YoY Change	6.63%	10.48%	8.98%

Cashflow Statement

Concept	2019 Q4	2019 Q3	2019 Q2
OPERATING ACTIVITIES
Net Income	$5.768M	$5.085M	$6.572M
YoY Change	41.93%	-4.07%	99.82%
Depreciation, Depletion And Amortization	$800.0K	$810.0K	$790.0K
YoY Change	110.53%	118.92%	113.51%
Cash From Operating Activities	$8.230M	$9.460M	$640.0K
YoY Change	65.26%	1.5%	-73.66%
INVESTING ACTIVITIES
Capital Expenditures	-$120.0K	-$100.0K	-$10.00K
YoY Change	-52.0%	-9.09%	-96.77%
Acquisitions
YoY Change
Other Investing Activities	-$6.860M	-$5.410M	-$63.49M
YoY Change	-67.19%	1219.51%	60.86%
Cash From Investing Activities	-$6.980M	-$5.510M	-$63.50M
YoY Change	-67.01%	959.62%	59.59%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	4.890M	11.14M	52.41M
YoY Change	-92.17%	-177.85%	139.86%
NET CHANGE
Cash From Operating Activities	8.230M	9.460M	640.0K
Cash From Investing Activities	-6.980M	-5.510M	-63.50M
Cash From Financing Activities	4.890M	11.14M	52.41M
Net Change In Cash	6.140M	15.09M	-10.45M
YoY Change	-86.72%	-373.87%	-32.62%
FREE CASH FLOW
Cash From Operating Activities	$8.230M	$9.460M	$640.0K
Capital Expenditures	-$120.0K	-$100.0K	-$10.00K
Free Cash Flow	$8.350M	$9.560M	$650.0K
YoY Change	59.66%	1.38%	-76.28%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0001521951
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	fbiz	New Market Tax Credit Benefit Periodof Recognition NewMarketTaxCreditBenefitPeriodofRecognition	P7Y
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity Filer Category EntityFilerCategory	Accelerated Filer
CY2020	dei	Entity File Number EntityFileNumber	001-34095
CY2020	dei	Entity Registrant Name EntityRegistrantName	FIRST BUSINESS FINANCIAL SERVICES, INC.
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	WI
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	39-1576570
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	401 Charmany Drive
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Madison
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	WI
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	53719
CY2020	dei	City Area Code CityAreaCode	608
CY2020	dei	Local Phone Number LocalPhoneNumber	238-8008
CY2020	dei	Security12b Title Security12bTitle	Common Stock, $0.01 par value
CY2020	dei	Trading Symbol TradingSymbol	FBIZ
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	No
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Small Business EntitySmallBusiness	true
CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
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CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.68
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.97
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.68
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.66
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.60
CY2020	us-gaap	Net Income Loss NetIncomeLoss	16978000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	23324000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	3526000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	2747000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-4000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-46000	USD
CY2020	fbiz	Other Comprehensive Income Loss Amortizationof Net Unrealized Losses Transferredto Heldto Maturityfrom Availablefor Salebeforetax OtherComprehensiveIncomeLossAmortizationofNetUnrealizedLossesTransferredtoHeldtoMaturityfromAvailableforSalebeforetax	39000	USD
CY2019	fbiz	Other Comprehensive Income Loss Amortizationof Net Unrealized Losses Transferredto Heldto Maturityfrom Availablefor Salebeforetax OtherComprehensiveIncomeLossAmortizationofNetUnrealizedLossesTransferredtoHeldtoMaturityfromAvailableforSalebeforetax	54000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Before Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax	-3011000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Before Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax	-2396000	USD
CY2020	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	143000	USD
CY2019	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	115000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	415000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	336000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	17393000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	23660000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	180707000	USD
CY2019	us-gaap	Income Tax Effects Allocated Directly To Equity Cumulative Effect Of Change In Accounting Principle IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple	687000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	23324000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	336000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1566000	USD
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	5216000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	7248000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	194156000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	16978000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	415000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	1871000	USD
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1672000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Employee Stock Purchase Program Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition	66000	USD
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	5652000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	206162000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	16978000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	23324000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2007000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2296000	USD
CY2020	fbiz	Impairmentof Tax Credit Investments ImpairmentofTaxCreditInvestments	2395000	USD
CY2019	fbiz	Impairmentof Tax Credit Investments ImpairmentofTaxCreditInvestments	4094000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	16808000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2085000	USD
CY2020	fbiz	Sba Recourse Provision SBARecourseProvision	-278000	USD
CY2019	fbiz	Sba Recourse Provision SBARecourseProvision	188000	USD
CY2020	fbiz	Derivative Credit Valuation Adjustment DerivativeCreditValuationAdjustment	461000	USD
CY2019	fbiz	Derivative Credit Valuation Adjustment DerivativeCreditValuationAdjustment	0	USD
CY2020	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	3465000	USD
CY2019	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	3049000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	1871000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	1566000	USD
CY2020	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-4000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-46000	USD
CY2020	fbiz	Gainon Saleof Historic Development Entity Tax Credit GainonSaleofHistoricDevelopmentEntityTaxCredit	275000	USD
CY2019	fbiz	Gainon Saleof Historic Development Entity Tax Credit GainonSaleofHistoricDevelopmentEntityTaxCredit	413000	USD
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1402000	USD
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1198000	USD
CY2020	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	81609000	USD
CY2019	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	61348000	USD
CY2020	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	81018000	USD
CY2019	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	62889000	USD
CY2020	us-gaap	Gain Loss On Sale Of Loans And Leases GainLossOnSaleOfLoansAndLeases	2899000	USD
CY2019	us-gaap	Gain Loss On Sale Of Loans And Leases GainLossOnSaleOfLoansAndLeases	1459000	USD
CY2020	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-383000	USD
CY2019	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	-224000	USD
CY2020	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	-16000	USD
CY2019	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	25000	USD
CY2020	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	0	USD
CY2019	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	299000	USD
CY2020	us-gaap	Excess Tax Benefit From Share Based Compensation Operating Activities ExcessTaxBenefitFromShareBasedCompensationOperatingActivities	32000	USD
CY2019	us-gaap	Excess Tax Benefit From Share Based Compensation Operating Activities ExcessTaxBenefitFromShareBasedCompensationOperatingActivities	102000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	1557000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	1527000	USD
CY2020	us-gaap	Proceeds From Lease Payments ProceedsFromLeasePayments	113000	USD
CY2019	us-gaap	Proceeds From Lease Payments ProceedsFromLeasePayments	9000	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable And Other Operating Assets IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets	10837000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable And Other Operating Assets IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets	15159000	USD
CY2020	us-gaap	Increase Decrease In Accrued Liabilities And Other Operating Liabilities IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities	4051000	USD
CY2019	us-gaap	Increase Decrease In Accrued Liabilities And Other Operating Liabilities IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities	14689000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	26635000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	28985000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	58290000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	30085000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	6268000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	4969000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	839000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	22452000	USD
CY2020	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	66879000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	84740000	USD
CY2020	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	2582000	USD
CY2019	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	0	USD
CY2020	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	439223000	USD
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	100444000	USD
CY2020	us-gaap	Payments To Acquire Limited Partnership Interests PaymentsToAcquireLimitedPartnershipInterests	1986000	USD
CY2019	us-gaap	Payments To Acquire Limited Partnership Interests PaymentsToAcquireLimitedPartnershipInterests	1250000	USD
CY2020	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	211000	USD
CY2019	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	2188000	USD
CY2020	fbiz	Paymentsto Acquire Historic Development Entities PaymentstoAcquireHistoricDevelopmentEntities	3254000	USD
CY2019	fbiz	Paymentsto Acquire Historic Development Entities PaymentstoAcquireHistoricDevelopmentEntities	8134000	USD
CY2020	fbiz	Distributionfromhistoricdevelopmententities Distributionfromhistoricdevelopmententities	30000	USD
CY2019	fbiz	Distributionfromhistoricdevelopmententities Distributionfromhistoricdevelopmententities	0	USD
CY2020	fbiz	Proceedsfrom Saleof Historic Development Entity State Tax Credits ProceedsfromSaleofHistoricDevelopmentEntityStateTaxCredits	2529000	USD
CY2019	fbiz	Proceedsfrom Saleof Historic Development Entity State Tax Credits ProceedsfromSaleofHistoricDevelopmentEntityStateTaxCredits	4340000	USD
CY2020	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	20509000	USD
CY2019	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	5943000	USD
CY2020	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	14884000	USD
CY2019	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	5230000	USD
CY2020	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	264000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	225000	USD
CY2020	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	8000000	USD
CY2019	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	0	USD
CY2020	fbiz	Premium Payment On Bank Owned Life Insurance Policies PremiumPaymentOnBankOwnedLifeInsurancePolicies	25000	USD
CY2019	fbiz	Premium Payment On Bank Owned Life Insurance Policies PremiumPaymentOnBankOwnedLifeInsurancePolicies	25000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-454507000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-131497000	USD
CY2020	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	325137000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	75080000	USD
CY2020	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	1219944000	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	536500000	USD
CY2020	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	1318700000	USD
CY2019	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	557000000	USD
CY2020	fbiz	Losson Early Extinguishmentof Debt Financing Activities LossonEarlyExtinguishmentofDebtFinancingActivities	744000	USD
CY2019	fbiz	Losson Early Extinguishmentof Debt Financing Activities LossonEarlyExtinguishmentofDebtFinancingActivities	0	USD
CY2020	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	0	USD
CY2019	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	15000000	USD
CY2020	us-gaap	Early Repayment Of Subordinated Debt EarlyRepaymentOfSubordinatedDebt	0	USD
CY2019	us-gaap	Early Repayment Of Subordinated Debt EarlyRepaymentOfSubordinatedDebt	15000000	USD
CY2020	fbiz	Payments Of The Federal Paycheck Protection Lending Facility Investing Activities PaymentsOfTheFederalPaycheckProtectionLendingFacilityInvestingActivities	29605000	USD
CY2019	fbiz	Payments Of The Federal Paycheck Protection Lending Facility Investing Activities PaymentsOfTheFederalPaycheckProtectionLendingFacilityInvestingActivities	0	USD
CY2020	fbiz	Proceedsfromthe Federal Paycheck Protection Program Lending Facility Investing Activities ProceedsfromtheFederalPaycheckProtectionProgramLendingFacilityInvestingActivities	29605000	USD
CY2019	fbiz	Proceedsfromthe Federal Paycheck Protection Program Lending Facility Investing Activities ProceedsfromtheFederalPaycheckProtectionProgramLendingFacilityInvestingActivities	0	USD
CY2020	us-gaap	Proceeds From Repayments Of Notes Payable ProceedsFromRepaymentsOfNotesPayable	300000	USD
CY2019	us-gaap	Proceeds From Repayments Of Notes Payable ProceedsFromRepaymentsOfNotesPayable	-48000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	5652000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	5216000	USD
CY2020	fbiz	Proceeds From Issuance Of Common Stock Under The Employee Stock Purchase Plan ProceedsFromIssuanceOfCommonStockUnderTheEmployeeStockPurchasePlan	66000	USD
CY2019	fbiz	Proceeds From Issuance Of Common Stock Under The Employee Stock Purchase Plan ProceedsFromIssuanceOfCommonStockUnderTheEmployeeStockPurchasePlan	0	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	1672000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	7248000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	417679000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	83068000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-10193000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-19444000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	67102000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	86546000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	56909000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	67102000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	18412000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	32999000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	3451000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	1294000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	190000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2020	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	80000	USD
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	596000	USD
CY2020	us-gaap	Use Of Estimates UseOfEstimates	Management of the Corporation is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements as well as reported amounts of revenues and expenses during the reporting period. Actual results could differ significantly from those estimates. Material estimates that could significantly change in the near-term include the value of securities and interest rate swaps, level of the allowance for loan and lease losses, lease residuals, property under operating leases, goodwill, level of the Small Business Administration (“SBA”) recourse reserve, and income taxes.
CY2020	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	Certain amounts in prior periods may have been reclassified to conform to the current presentation.
CY2020Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	8700000	USD
CY2019Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	5200000	USD
CY2020Q4	fbiz	Bank Owned Life Insurance Death Benefits BankOwnedLifeInsuranceDeathBenefits	136100000	USD
CY2019Q4	fbiz	Bank Owned Life Insurance Death Benefits BankOwnedLifeInsuranceDeathBenefits	97900000	USD
CY2019Q4	fbiz	Borrowings Against Cash Surrender Value Of Bank Owned Life Insurance BorrowingsAgainstCashSurrenderValueOfBankOwnedLifeInsurance	0	USD
CY2020Q4	fbiz	Borrowings Against Cash Surrender Value Of Bank Owned Life Insurance BorrowingsAgainstCashSurrenderValueOfBankOwnedLifeInsurance	0	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	13600000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	8000000.0	USD
CY2020	fbiz	Maximum Ownership Percentage That Is Not Consolidated MaximumOwnershipPercentageThatIsNotConsolidated	0.50
CY2020	fbiz	Investment In Corporations Minimum Ownership Percentage For Accounting For Using Equity Method InvestmentInCorporationsMinimumOwnershipPercentageForAccountingForUsingEquityMethod	0.20
CY2020	fbiz	Investment In Corporations Maximum Ownership Percentage For Accounting For At Cost InvestmentInCorporationsMaximumOwnershipPercentageForAccountingForAtCost	0.20
CY2020	fbiz	Investment In Limited Partnerships Maximum Ownership Percentage For Accounting For At Cost InvestmentInLimitedPartnershipsMaximumOwnershipPercentageForAccountingForAtCost	0.03
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-4000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-46000	USD
CY2020	fbiz	Increasein Loansand Leases Receivable Allowance IncreaseinLoansandLeasesReceivableAllowance	9000000.0	USD
CY2020	fbiz	Percent Increasein Loansand Leases Receivable Allowance PercentIncreaseinLoansandLeasesReceivableAllowance	0.461
CY2020	fbiz	Financing Receivable Allowancefor Credit Losses Increasedueto Economic Conditions FinancingReceivableAllowanceforCreditLossesIncreaseduetoEconomicConditions	5500000	USD
CY2020	fbiz	Financing Receivable Allowance For Credit Loss Increase Due To Loan Growth FinancingReceivableAllowanceForCreditLossIncreaseDueToLoanGrowth	2300000	USD
CY2020	fbiz	Financing Receivable Allowance For Credit Losses Increase Due To Historic Loss Rate Updates FinancingReceivableAllowanceForCreditLossesIncreaseDueToHistoricLossRateUpdates	949000	USD
CY2020Q4	fbiz	Numberof Short Term Loan Modifications NumberofShortTermLoanModifications	38
CY2020Q4	fbiz	Gross Loansand Leases Outstanding Short Term Modification GrossLoansandLeasesOutstandingShortTermModification	27000000.0	USD
CY2020Q4	fbiz	Gross Loansand Leases Outstanding Short Term Modification Percent6 Month Deferral Period GrossLoansandLeasesOutstandingShortTermModificationPercent6MonthDeferralPeriod	0.014
CY2020Q3	fbiz	Gross Loansand Leases Outstanding Short Term Modification GrossLoansandLeasesOutstandingShortTermModification	131500000	USD
CY2020Q3	fbiz	Gross Loansand Leases Outstanding Short Term Modification Percent6 Month Deferral Period GrossLoansandLeasesOutstandingShortTermModificationPercent6MonthDeferralPeriod	0.071
CY2020Q4	fbiz	Sba Paycheck Protection Program Loans Outstanding Gross Amount SBAPaycheckProtectionProgramLoansOutstandingGrossAmount	228900000	USD
CY2020Q4	fbiz	Sba Paycheck Protection Program Loan Leases Receiveable Deferred Income SBAPaycheckProtectionProgramLoanLeasesReceiveableDeferredIncome	3500000	USD
CY2020Q4	fbiz	Sba Paycheck Protection Program Interest Income Loans SBAPaycheckProtectionProgramInterestIncomeLoans	5300000	USD
CY2020Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	29500000	USD
CY2019Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	16100000	USD
CY2019Q4	fbiz	Required Reserves In Form Of Either Vault Cash Or Deposits Held At Federal Reserve Bank RequiredReservesInFormOfEitherVaultCashOrDepositsHeldAtFederalReserveBank	9200000	USD
CY2020Q4	fbiz	Balances Held At Federal Reserve BalancesHeldAtFederalReserve	26700000	USD
CY2019Q4	fbiz	Balances Held At Federal Reserve BalancesHeldAtFederalReserve	44400000	USD
CY2020Q4	us-gaap	Interest Bearing Deposits In Banks InterestBearingDepositsInBanks	27400000	USD
CY2019Q4	us-gaap	Interest Bearing Deposits In Banks InterestBearingDepositsInBanks	51000000.0	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	179581000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	4476000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	132000	USD
CY2020Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	183925000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	172319000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	1331000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	517000	USD
CY2019Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	173133000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	26374000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	974000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	15000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	27333000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	32700000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	30300000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	528000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	40000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	33188000	USD
CY2020	fbiz	Numberofavailableforsalesecuritiessold Numberofavailableforsalesecuritiessold	1	securities
CY2019	fbiz	Numberofavailableforsalesecuritiessold Numberofavailableforsalesecuritiessold	69	securities
CY2020	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	0	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	58000	USD
CY2020	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	4000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	104000	USD
CY2020	us-gaap	Marketable Securities Realized Gain Loss MarketableSecuritiesRealizedGainLoss	-4000	USD
CY2019	us-gaap	Marketable Securities Realized Gain Loss MarketableSecuritiesRealizedGainLoss	-46000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	839000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	22452000	USD
CY2020Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	73700000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Next Rolling Twelve Months Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis	0	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Next Rolling Twelve Months Fair Value AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue	0	USD
CY2020Q4	us-gaap	Heldtomaturity Securities Debt Maturities Next Rolling Twelve Months Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost	2299000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Next Rolling Twelve Months Fair Value HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue	2311000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Two Through Five Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis	8869000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Two Through Five Fair Value AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue	9128000	USD
CY2020Q4	fbiz	Heldtomaturity Securities Debt Maturities Rolling Years Two Through Five Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesRollingYearsTwoThroughFiveAmortizedCost	12110000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Rolling Year Two Through Five Fair Value HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue	12353000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Six Through Ten Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis	38114000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling Year Six Through Ten Fair Value AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue	39642000	USD
CY2020Q4	fbiz	Heldtomaturity Securities Debt Maturities Rolling Years Six Through Ten Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesRollingYearsSixThroughTenAmortizedCost	9423000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Rolling Year Six Through Ten Fair Value HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue	10005000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling After Year Ten Amortized Cost Basis AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis	132598000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Rolling After Year Ten Fair Value AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue	135155000	USD
CY2020Q4	us-gaap	Heldtomaturity Securities Debt Maturities Rolling After Ten Years Amortized Cost HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost	2542000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Rolling After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesRollingAfterTenYearsFairValue	2664000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	179581000	USD
CY2020Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	183925000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	26374000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	27333000	USD
CY2020Q4	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	14	securities
CY2020Q4	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Greater Than Or Equal To One Year AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear	1	securities
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Availableforsale Securities OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities	0	USD
CY2020	us-gaap	Other Than Temporary Impairment Losses Investments Availableforsale Securities OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities	0	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	33543000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	98000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	4031000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	34000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	37574000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	132000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	48199000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	272000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	17078000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	245000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	65277000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	517000	USD
CY2020Q4	us-gaap	Held To Maturity Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions	2	securities
CY2020Q4	fbiz	Heldto Maturity Securities Securitiesin Unrealized Loss Positions Qualitative Disclosures Numberof Positions12monthsorgreater HeldtoMaturitySecuritiesSecuritiesinUnrealizedLossPositionsQualitativeDisclosuresNumberofPositions12monthsorgreater	1	securities
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Heldtomaturity Securities OtherThanTemporaryImpairmentLossesInvestmentsHeldtomaturitySecurities	0	USD
CY2020	us-gaap	Other Than Temporary Impairment Losses Investments Heldtomaturity Securities OtherThanTemporaryImpairmentLossesInvestmentsHeldtomaturitySecurities	0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	1863000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	13000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	4031000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	27000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	5894000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	40000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Before Fees Gross LoansAndLeasesReceivableBeforeFeesGross	2150515000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Before Fees Gross LoansAndLeasesReceivableBeforeFeesGross	1715265000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	28521000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	19520000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	4545000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	630000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	2117449000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	1695115000	USD
CY2020Q4	fbiz	Sba Paycheck Protection Program Loans Outstanding Gross Amount SBAPaycheckProtectionProgramLoansOutstandingGrossAmount	228900000	USD
CY2020Q4	fbiz	Paycheck Protection Loans And Leases Receivable Deferred Income PaycheckProtectionLoansAndLeasesReceivableDeferredIncome	3500000	USD
CY2020Q4	fbiz	Small Business Administration7a Loans SmallBusinessAdministration7aLoans	36266000	USD
CY2019Q4	fbiz	Small Business Administration7a Loans SmallBusinessAdministration7aLoans	40402000	USD
CY2020Q4	fbiz	Small Business Administration504 Loans SmallBusinessAdministration504Loans	26327000	USD
CY2019Q4	fbiz	Small Business Administration504 Loans SmallBusinessAdministration504Loans	20592000	USD
CY2020Q4	fbiz	Small Business Administration Express Loans SmallBusinessAdministrationExpressLoans	1251000	USD
CY2019Q4	fbiz	Small Business Administration Express Loans SmallBusinessAdministrationExpressLoans	1781000	USD
CY2020Q4	fbiz	Small Business Administration Paycheck Protection Program Loans SmallBusinessAdministrationPaycheckProtectionProgramLoans	228870000	USD
CY2019Q4	fbiz	Small Business Administration Paycheck Protection Program Loans SmallBusinessAdministrationPaycheckProtectionProgramLoans	0	USD
CY2020Q4	fbiz	Small Business Administration Loans SmallBusinessAdministrationLoans	292714000	USD
CY2019Q4	fbiz	Small Business Administration Loans SmallBusinessAdministrationLoans	62775000	USD
CY2020Q4	fbiz	Sb Aloansintheparticipationsoldportfolioconsideredimpaired SBAloansintheparticipationsoldportfolioconsideredimpaired	9300000	USD
CY2019Q4	fbiz	Sb Aloansintheparticipationsoldportfolioconsideredimpaired SBAloansintheparticipationsoldportfolioconsideredimpaired	12100000	USD
CY2020	fbiz	Guaranteed Portionof Sba Loans Soldto Third Parties Total GuaranteedPortionofSBALoansSoldtoThirdPartiesTotal	29200000	USD
CY2019	fbiz	Guaranteed Portionof Sba Loans Soldto Third Parties Total GuaranteedPortionofSBALoansSoldtoThirdPartiesTotal	16100000	USD
CY2020Q4	fbiz	Totalamountofoutstanding Sb Aloanssold TotalamountofoutstandingSBAloanssold	79500000	USD
CY2019Q4	fbiz	Totalamountofoutstanding Sb Aloanssold TotalamountofoutstandingSBAloanssold	73800000	USD
CY2020	fbiz	Loans And Leases Transferred To Third Parties Total Principal Amount LoansAndLeasesTransferredToThirdPartiesTotalPrincipalAmount	48900000	USD
CY2020Q4	fbiz	Loans And Leases Transferred To Third Parties Total Principal Amount LoansAndLeasesTransferredToThirdPartiesTotalPrincipalAmount	45400000	USD
CY2020	fbiz	Gain Loss Recognizedon Participation Interestin Originated Loans GainLossRecognizedonParticipationInterestinOriginatedLoans	0	USD
CY2020Q4	fbiz	Total Amount Of Outstanding Loans Transferred To Third Parties As Loan Participations TotalAmountOfOutstandingLoansTransferredToThirdPartiesAsLoanParticipations	153600000	USD
CY2019Q4	fbiz	Total Amount Of Outstanding Loans Transferred To Third Parties As Loan Participations TotalAmountOfOutstandingLoansTransferredToThirdPartiesAsLoanParticipations	142800000	USD
CY2020Q4	fbiz	Total Amount Of Loan Participations Remaining On Corporations Balance Sheet TotalAmountOfLoanParticipationsRemainingOnCorporationsBalanceSheet	276500000	USD
CY2019Q4	fbiz	Total Amount Of Loan Participations Remaining On Corporations Balance Sheet TotalAmountOfLoanParticipationsRemainingOnCorporationsBalanceSheet	244600000	USD
CY2020Q4	fbiz	Loans In Participation Sold Portfolio Considered Impaired LoansInParticipationSoldPortfolioConsideredImpaired	3000000.0	USD
CY2020Q4	fbiz	Loans In The Participation Sold Portfolio Considered Impaired Sold Amount LoansInTheParticipationSoldPortfolioConsideredImpairedSoldAmount	4200000	USD
CY2020Q4	fbiz	Loans In The Participation Sold Portfolio Considered Impaired Charged Off Amount LoansInTheParticipationSoldPortfolioConsideredImpairedChargedOffAmount	2800000	USD
CY2019Q4	fbiz	Loans In The Participation Sold Portfolio Considered Impaired Charged Off Amount LoansInTheParticipationSoldPortfolioConsideredImpairedChargedOffAmount	0	USD
CY2020Q4	fbiz	Loan Participations Purchased On Corporations Balance Sheet LoanParticipationsPurchasedOnCorporationsBalanceSheet	410000	USD
CY2019Q4	fbiz	Loan Participations Purchased On Corporations Balance Sheet LoanParticipationsPurchasedOnCorporationsBalanceSheet	492000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	1683000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	1855000	USD
CY2020	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	325000	USD
CY2019	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	412000	USD
CY2020	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	376000	USD
CY2019	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	584000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	1632000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	1683000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Before Fees Gross LoansAndLeasesReceivableBeforeFeesGross	2150515000	USD
CY2020Q4	fbiz	Category Rating As Percentage Of Total Loans And Leases CategoryRatingAsPercentageOfTotalLoansAndLeases	1.0000
CY2019Q4	us-gaap	Loans And Leases Receivable Before Fees Gross LoansAndLeasesReceivableBeforeFeesGross	1715265000	USD
CY2019Q4	fbiz	Category Rating As Percentage Of Total Loans And Leases CategoryRatingAsPercentageOfTotalLoansAndLeases	1.0000
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	21572000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	2128943000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	2150515000	USD
CY2020Q4	fbiz	Financing Receivable Recorded Investment30 To59 Days Past Due Percent Of Portfolio FinancingReceivableRecordedInvestment30To59DaysPastDuePercentOfPortfolio	0.0044
CY2020Q4	fbiz	Financing Receivable Recorded Investment60 To89 Days Past Due Percent Of Portfolio FinancingReceivableRecordedInvestment60To89DaysPastDuePercentOfPortfolio	0.0002
CY2020Q4	fbiz	Financing Receivable Recorded Investment Equal To Greater Than90 Days Past Due Percent Of Portfolio FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDuePercentOfPortfolio	0.0054
CY2020Q4	fbiz	Financing Receivable Recorded Investment Past Due Percent Of Portfolio FinancingReceivableRecordedInvestmentPastDuePercentOfPortfolio	0.0100
CY2020Q4	fbiz	Financing Receivable Recorded Investment Current Percent Of Portfolio FinancingReceivableRecordedInvestmentCurrentPercentOfPortfolio	0.9900
CY2020Q4	fbiz	Financing Receivable Recorded Investment Gross Percent Of Portfolio FinancingReceivableRecordedInvestmentGrossPercentOfPortfolio	1.0000
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	15088000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	1700177000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	1715265000	USD
CY2019Q4	fbiz	Financing Receivable Recorded Investment30 To59 Days Past Due Percent Of Portfolio FinancingReceivableRecordedInvestment30To59DaysPastDuePercentOfPortfolio	0.0043
CY2019Q4	fbiz	Financing Receivable Recorded Investment60 To89 Days Past Due Percent Of Portfolio FinancingReceivableRecordedInvestment60To89DaysPastDuePercentOfPortfolio	0.0024
CY2019Q4	fbiz	Financing Receivable Recorded Investment Equal To Greater Than90 Days Past Due Percent Of Portfolio FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDuePercentOfPortfolio	0.0021
CY2019Q4	fbiz	Financing Receivable Recorded Investment Past Due Percent Of Portfolio FinancingReceivableRecordedInvestmentPastDuePercentOfPortfolio	0.0088
CY2019Q4	fbiz	Financing Receivable Recorded Investment Current Percent Of Portfolio FinancingReceivableRecordedInvestmentCurrentPercentOfPortfolio	0.9912
CY2019Q4	fbiz	Financing Receivable Recorded Investment Gross Percent Of Portfolio FinancingReceivableRecordedInvestmentGrossPercentOfPortfolio	1.0000
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	26617000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	20613000	USD
CY2020Q4	us-gaap	Foreclosed Assets ForeclosedAssets	34000	USD
CY2019Q4	us-gaap	Foreclosed Assets ForeclosedAssets	2919000	USD
CY2020Q4	fbiz	Total Nonperforming Assets TotalNonperformingAssets	26651000	USD
CY2019Q4	fbiz	Total Nonperforming Assets TotalNonperformingAssets	23532000	USD
CY2020Q4	fbiz	Financing Receivable Modifications Performing Troubled Debt Restructuring FinancingReceivableModificationsPerformingTroubledDebtRestructuring	46000	USD
CY2019Q4	fbiz	Financing Receivable Modifications Performing Troubled Debt Restructuring FinancingReceivableModificationsPerformingTroubledDebtRestructuring	140000	USD
CY2020Q4	fbiz	Impaired Assets ImpairedAssets	26697000	USD
CY2019Q4	fbiz	Impaired Assets ImpairedAssets	23672000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Ratio Of Nonperforming Loans To All Loans LoansAndLeasesReceivableRatioOfNonperformingLoansToAllLoans	0.0124
CY2019Q4	us-gaap	Loans And Leases Receivable Ratio Of Nonperforming Loans To All Loans LoansAndLeasesReceivableRatioOfNonperformingLoansToAllLoans	0.0120
CY2020Q4	fbiz	Ratio Of Total Nonperforming Assets To Gross Loans And Leases Plus Foreclosed Properties Net RatioOfTotalNonperformingAssetsToGrossLoansAndLeasesPlusForeclosedPropertiesNet	0.0124
CY2019Q4	fbiz	Ratio Of Total Nonperforming Assets To Gross Loans And Leases Plus Foreclosed Properties Net RatioOfTotalNonperformingAssetsToGrossLoansAndLeasesPlusForeclosedPropertiesNet	0.0137
CY2020Q4	fbiz	Ratio Of Total Nonperforming Assets To Total Assets RatioOfTotalNonperformingAssetsToTotalAssets	0.0104
CY2019Q4	fbiz	Ratio Of Total Nonperforming Assets To Total Assets RatioOfTotalNonperformingAssetsToTotalAssets	0.0112
CY2020Q4	fbiz	Ratio Of Allowance For Loan And Lease Losses To Total Gross Loans And Leases RatioOfAllowanceForLoanAndLeaseLossesToTotalGrossLoansAndLeases	0.0133
CY2019Q4	fbiz	Ratio Of Allowance For Loan And Lease Losses To Total Gross Loans And Leases RatioOfAllowanceForLoanAndLeaseLossesToTotalGrossLoansAndLeases	0.0114
CY2020Q4	fbiz	Ratio Of Allowance For Loan And Leases Losses To Non Accrual Loans And Leases RatioOfAllowanceForLoanAndLeasesLossesToNonAccrualLoansAndLeases	1.0715
CY2019Q4	fbiz	Ratio Of Allowance For Loan And Leases Losses To Non Accrual Loans And Leases RatioOfAllowanceForLoanAndLeasesLossesToNonAccrualLoansAndLeases	0.9470
CY2020Q4	fbiz	Non Accrual Troubled Debt Restructurings NonAccrualTroubledDebtRestructurings	6500000	USD
CY2019Q4	fbiz	Non Accrual Troubled Debt Restructurings NonAccrualTroubledDebtRestructurings	15600000	USD
CY2020Q4	fbiz	Specific Reserveson Troubled Debt Restructurings SpecificReservesonTroubledDebtRestructurings	760000	USD
CY2019Q4	fbiz	Specific Reserveson Troubled Debt Restructurings SpecificReservesonTroubledDebtRestructurings	2700000	USD
CY2020Q4	fbiz	Unfunded Commitments Troubled Debt Restructurings UnfundedCommitmentsTroubledDebtRestructurings	0	USD
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	5	loans
CY2020	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	6306000	USD
CY2020	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	889000	USD
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	17	loans
CY2019	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	17146000	USD
CY2019	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	13459000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	18966000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance	29191000	USD
CY2020	us-gaap	Impaired Financing Receivable With No Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment	21709000	USD
CY2020	fbiz	Impaired Financing Receivable With No Related Allowance Foregone Interest Income ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome	2082000	USD
CY2020	us-gaap	Impaired Financing Receivable With No Related Allowance Interest Income Cash Basis Method ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod	636000	USD
CY2020	fbiz	Impaired Financing Receivable With No Related Allowance Net Foregone Interest Income ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome	1446000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	7697000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable With Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance	12103000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	3681000	USD
CY2020	us-gaap	Impaired Financing Receivable With Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment	5994000	USD
CY2020	fbiz	Impaired Financing Receivable With Related Allowance Foregone Interest Income ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome	712000	USD
CY2020	us-gaap	Impaired Financing Receivable With Related Allowance Interest Income Cash Basis Method ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod	0	USD
CY2020	fbiz	Impaired Financing Receivable With Related Allowance Net Foregone Interest Income ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome	712000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	26663000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	41294000	USD
CY2020Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	3681000	USD
CY2020	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	27703000	USD
CY2020	fbiz	Impaired Financing Receivable Foregone Interest Income ImpairedFinancingReceivableForegoneInterestIncome	2794000	USD
CY2020	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	636000	USD
CY2020	fbiz	Impaired Financing Receivable Net Foregone Interest Income ImpairedFinancingReceivableNetForegoneInterestIncome	2158000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	7312000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance	14050000	USD
CY2019	us-gaap	Impaired Financing Receivable With No Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment	20212000	USD
CY2019	fbiz	Impaired Financing Receivable With No Related Allowance Foregone Interest Income ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome	1257000	USD
CY2019	us-gaap	Impaired Financing Receivable With No Related Allowance Interest Income Cash Basis Method ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod	793000	USD
CY2019	fbiz	Impaired Financing Receivable With No Related Allowance Net Foregone Interest Income ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome	464000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	13441000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance	16183000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	3365000	USD
CY2019	us-gaap	Impaired Financing Receivable With Related Allowance Average Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment	3878000	USD
CY2019	fbiz	Impaired Financing Receivable With Related Allowance Foregone Interest Income ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome	1436000	USD
CY2019	us-gaap	Impaired Financing Receivable With Related Allowance Interest Income Cash Basis Method ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod	0	USD
CY2019	fbiz	Impaired Financing Receivable With Related Allowance Net Foregone Interest Income ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome	1436000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	20753000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	30233000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	3365000	USD
CY2019	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	24090000	USD
CY2019	fbiz	Impaired Financing Receivable Foregone Interest Income ImpairedFinancingReceivableForegoneInterestIncome	2693000	USD
CY2019	us-gaap	Impaired Financing Receivable Interest Income Cash Basis Method ImpairedFinancingReceivableInterestIncomeCashBasisMethod	793000	USD
CY2019	fbiz	Impaired Financing Receivable Net Foregone Interest Income ImpairedFinancingReceivableNetForegoneInterestIncome	1900000	USD
CY2020Q4	fbiz	Loans And Leases Receivable Difference Between Recorded Investment And Unpaid Principal Balance LoansAndLeasesReceivableDifferenceBetweenRecordedInvestmentAndUnpaidPrincipalBalance	14600000	USD
CY2019Q4	fbiz	Loans And Leases Receivable Difference Between Recorded Investment And Unpaid Principal Balance LoansAndLeasesReceivableDifferenceBetweenRecordedInvestmentAndUnpaidPrincipalBalance	9500000	USD
CY2020Q4	fbiz	Financing Receivable Modifications Performing Troubled Debt Restructuring FinancingReceivableModificationsPerformingTroubledDebtRestructuring	46000	USD
CY2019Q4	fbiz	Financing Receivable Modifications Performing Troubled Debt Restructuring FinancingReceivableModificationsPerformingTroubledDebtRestructuring	140000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	19520000	USD
CY2020	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	8139000	USD
CY2020	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	332000	USD
CY2020	us-gaap	Allowance For Loan And Lease Losses Writeoffs Net AllowanceForLoanAndLeaseLossesWriteoffsNet	-7807000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	16808000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	28521000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	20425000	USD
CY2019	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	3356000	USD
CY2019	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	366000	USD
CY2019	us-gaap	Allowance For Loan And Lease Losses Writeoffs Net AllowanceForLoanAndLeaseLossesWriteoffsNet	-2990000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	2085000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	19520000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	24840000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	3681000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	28521000	USD
CY2020Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	2123852000	USD
CY2020Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	26663000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	2150515000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	16155000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	3365000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	19520000	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	1694512000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	20753000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	1715265000	USD
CY2020Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Minimum Payments To Be Received CapitalLeasesNetInvestmentInDirectFinancingLeasesMinimumPaymentsToBeReceived	19106000	USD
CY2019Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Minimum Payments To Be Received CapitalLeasesNetInvestmentInDirectFinancingLeasesMinimumPaymentsToBeReceived	24165000	USD
CY2020Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Unguaranteed Residual Values Of Leased Property CapitalLeasesNetInvestmentInDirectFinancingLeasesUnguaranteedResidualValuesOfLeasedProperty	5434000	USD
CY2019Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Unguaranteed Residual Values Of Leased Property CapitalLeasesNetInvestmentInDirectFinancingLeasesUnguaranteedResidualValuesOfLeasedProperty	6732000	USD
CY2020Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Deferred Income CapitalLeasesNetInvestmentInDirectFinancingLeasesDeferredIncome	2209000	USD
CY2019Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Deferred Income CapitalLeasesNetInvestmentInDirectFinancingLeasesDeferredIncome	2805000	USD
CY2020Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases CapitalLeasesNetInvestmentInDirectFinancingLeases	22331000	USD
CY2019Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases CapitalLeasesNetInvestmentInDirectFinancingLeases	28092000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable Current CapitalLeasesFutureMinimumPaymentsReceivableCurrent	6467000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable In Two Years CapitalLeasesFutureMinimumPaymentsReceivableInTwoYears	5332000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable In Three Years CapitalLeasesFutureMinimumPaymentsReceivableInThreeYears	3797000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable In Four Years CapitalLeasesFutureMinimumPaymentsReceivableInFourYears	2262000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable In Five Years CapitalLeasesFutureMinimumPaymentsReceivableInFiveYears	1036000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable Due Thereafter CapitalLeasesFutureMinimumPaymentsReceivableDueThereafter	212000	USD
CY2020Q4	us-gaap	Capital Leases Future Minimum Payments Receivable CapitalLeasesFutureMinimumPaymentsReceivable	19106000	USD
CY2020Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	2670000	USD
CY2019Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	2670000	USD
CY2020Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	6961000	USD
CY2019Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	6718000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	9631000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	9388000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	7633000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	6831000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	1998000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2557000	USD
CY2020	us-gaap	Depreciation Depreciation	822000	USD
CY2019	us-gaap	Depreciation Depreciation	877000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	190000	USD
CY2020	us-gaap	Operating Lease Expense OperatingLeaseExpense	1494000	USD
CY2019	us-gaap	Operating Lease Expense OperatingLeaseExpense	1551000	USD
CY2020	us-gaap	Short Term Lease Cost ShortTermLeaseCost	222000	USD
CY2019	us-gaap	Short Term Lease Cost ShortTermLeaseCost	257000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	522000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	493000	USD
CY2020	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	113000	USD
CY2019	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	9000	USD
CY2020	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	2125000	USD
CY2019	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	2292000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P5Y9M18D
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y6M21D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0303
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0309
CY2020Q4	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	1557000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	1373000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	1015000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	756000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	666000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	1641000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	7008000	USD
CY2020Q4	fbiz	Discountonoperatingleasecashflows Discountonoperatingleasecashflows	622000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	6386000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	10700000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	10700000	USD
CY2020Q3	us-gaap	Equity Fair Value Disclosure EquityFairValueDisclosure	289000000.0	USD
CY2020Q3	us-gaap	Reporting Unit Amount Of Fair Value In Excess Of Carrying Amount ReportingUnitAmountOfFairValueInExcessOfCarryingAmount	89400000	USD
CY2020Q3	us-gaap	Reporting Unit Percentage Of Fair Value In Excess Of Carrying Amount ReportingUnitPercentageOfFairValueInExcessOfCarryingAmount	0.448
CY2020	us-gaap	Servicing Asset At Amortized Value Amortization1 ServicingAssetAtAmortizedValueAmortization1	458000	USD
CY2019	us-gaap	Servicing Asset At Amortized Value Amortization1 ServicingAssetAtAmortizedValueAmortization1	374000	USD
CY2020Q4	us-gaap	Servicing Asset At Fair Value Amount ServicingAssetAtFairValueAmount	1300000	USD
CY2019Q4	us-gaap	Servicing Asset At Fair Value Amount ServicingAssetAtFairValueAmount	1200000	USD
CY2020Q4	fbiz	Investmentin Historic Development Entities InvestmentinHistoricDevelopmentEntities	2400000	USD
CY2019Q4	fbiz	Investmentin Historic Development Entities InvestmentinHistoricDevelopmentEntities	2200000	USD
CY2020	fbiz	Capital Contributionsto Historic Rehabilitation Tax Credits CapitalContributionstoHistoricRehabilitationTaxCredits	4400000	USD
CY2020	fbiz	Tax Credit Benefits Recognizedon Federal Historic Tax Credits TaxCreditBenefitsRecognizedonFederalHistoricTaxCredits	2800000	USD
CY2020	fbiz	Expense Relatedto Investmentin Historic Rehabilitation Tax Credits ExpenseRelatedtoInvestmentinHistoricRehabilitationTaxCredits	1900000	USD
CY2019	fbiz	Capital Contributionsto Historic Rehabilitation Tax Credits CapitalContributionstoHistoricRehabilitationTaxCredits	9400000	USD
CY2019	fbiz	Tax Credit Benefits Recognizedon Federal Historic Tax Credits TaxCreditBenefitsRecognizedonFederalHistoricTaxCredits	5200000	USD
CY2019	fbiz	Expense Relatedto Investmentin Historic Rehabilitation Tax Credits ExpenseRelatedtoInvestmentinHistoricRehabilitationTaxCredits	3600000	USD
CY2020	fbiz	Tax Credit Benefits Recognized On State Historic Tax Credits TaxCreditBenefitsRecognizedOnStateHistoricTaxCredits	2700000	USD
CY2019	fbiz	Tax Credit Benefits Recognized On State Historic Tax Credits TaxCreditBenefitsRecognizedOnStateHistoricTaxCredits	4700000	USD
CY2020	fbiz	Gainon Saleof Historic Development Entities GainonSaleofHistoricDevelopmentEntities	275000	USD
CY2019	fbiz	Gainon Saleof Historic Development Entities GainonSaleofHistoricDevelopmentEntities	413000	USD
CY2020Q4	fbiz	Investmentin Community Development Entities InvestmentinCommunityDevelopmentEntities	5300000	USD
CY2019Q4	fbiz	Investmentin Community Development Entities InvestmentinCommunityDevelopmentEntities	5600000	USD
CY2019	fbiz	Tax Credit Benefits Recognizedon New Market Tax Credits TaxCreditBenefitsRecognizedonNewMarketTaxCredits	450000	USD
CY2020	fbiz	Tax Credit Benefits Recognizedon New Market Tax Credits TaxCreditBenefitsRecognizedonNewMarketTaxCredits	450000	USD
CY2020	fbiz	Losson Equity Method Investments LossonEquityMethodInvestments	99000	USD
CY2020Q4	fbiz	Losson Equity Method Investments LossonEquityMethodInvestments	121000	USD
CY2020	fbiz	Incomefrom Equity Method Investments IncomefromEquityMethodInvestments	520000	USD
CY2020Q4	fbiz	Incomefrom Equity Method Investments IncomefromEquityMethodInvestments	1400000	USD
CY2020	fbiz	Losson Equity Method Investments LossonEquityMethodInvestments	0	USD
CY2020Q4	fbiz	Investmentin Trust Ii InvestmentinTrustII	315000	USD
CY2020Q4	us-gaap	Interest Receivable InterestReceivable	8564000	USD
CY2019Q4	us-gaap	Interest Receivable InterestReceivable	5760000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	7217000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	5353000	USD
CY2020Q4	fbiz	Investmentin Historic Development Entities InvestmentinHistoricDevelopmentEntities	2356000	USD
CY2019Q4	fbiz	Investmentin Historic Development Entities InvestmentinHistoricDevelopmentEntities	2216000	USD
CY2020Q4	fbiz	Investmentin Community Development Entities InvestmentinCommunityDevelopmentEntities	5306000	USD
CY2019Q4	fbiz	Investmentin Community Development Entities InvestmentinCommunityDevelopmentEntities	5571000	USD
CY2020Q4	fbiz	Investmentin Limited Partnerships InvestmentinLimitedPartnerships	6673000	USD
CY2019Q4	fbiz	Investmentin Limited Partnerships InvestmentinLimitedPartnerships	4476000	USD
CY2020Q4	fbiz	Investmentin Trust Ii InvestmentinTrustII	315000	USD
CY2019Q4	fbiz	Investmentin Trust Ii InvestmentinTrustII	315000	USD
CY2020Q4	us-gaap	Prepaid Expense Current And Noncurrent PrepaidExpenseCurrentAndNoncurrent	2165000	USD
CY2019Q4	us-gaap	Prepaid Expense Current And Noncurrent PrepaidExpenseCurrentAndNoncurrent	2285000	USD
CY2020Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	6882000	USD
CY2019Q4	us-gaap	Other Assets Miscellaneous OtherAssetsMiscellaneous	4184000	USD
CY2020Q4	us-gaap	Other Assets OtherAssets	39478000	USD
CY2019Q4	us-gaap	Other Assets OtherAssets	30160000	USD
CY2020Q4	us-gaap	Deposits Deposits	1855516000	USD
CY2020	fbiz	Average Balance Deposits AverageBalanceDeposits	1711092000	USD
CY2020	fbiz	Deposits Weighted Average Interest Rate Duringthe Period DepositsWeightedAverageInterestRateDuringthePeriod	0.0052
CY2019Q4	us-gaap	Deposits Deposits	1530379000	USD
CY2019	fbiz	Average Balance Deposits AverageBalanceDeposits	1496430000	USD
CY2019	fbiz	Deposits Weighted Average Interest Rate Duringthe Period DepositsWeightedAverageInterestRateDuringthePeriod	0.0153
CY2020Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	101722000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	6199000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	1239000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	263000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	1735000	USD
CY2020Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	1044000	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	112202000	USD
CY2020Q4	fbiz	Time Deposits250000or More TimeDeposits250000orMore	28700000	USD
CY2019Q4	fbiz	Time Deposits250000or More TimeDeposits250000orMore	63700000	USD
CY2020Q4	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	429229000	USD
CY2020	fbiz	Borrowed Funds Average Balance BorrowedFundsAverageBalance	429624000	USD
CY2020	us-gaap	Debt Instrument Interest Rate During Period DebtInstrumentInterestRateDuringPeriod	0.0191
CY2019Q4	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	329429000	USD
CY2019	fbiz	Borrowed Funds Average Balance BorrowedFundsAverageBalance	321740000	USD
CY2019	us-gaap	Debt Instrument Interest Rate During Period DebtInstrumentInterestRateDuringPeriod	0.0287
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	210000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	29000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	7000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	25500000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	13000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	144729000	USD
CY2020Q4	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	429229000	USD
CY2020Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Loans Receivable Pledged For Federal Home Loan Bank Debt PledgedFinancialInstrumentsNotSeparatelyReportedLoansReceivablePledgedForFederalHomeLoanBankDebt	644600000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Loans Receivable Pledged For Federal Home Loan Bank Debt PledgedFinancialInstrumentsNotSeparatelyReportedLoansReceivablePledgedForFederalHomeLoanBankDebt	507600000	USD
CY2020	us-gaap	Line Of Credit Facility Commitment Fee Amount LineOfCreditFacilityCommitmentFeeAmount	13000	USD
CY2020Q4	fbiz	Unamortized Debt Issuance Cost Subordinated Notes UnamortizedDebtIssuanceCostSubordinatedNotes	343000	USD
CY2020Q4	fbiz	Sole Ownership Of Common Securities Issued By Trust Ii SoleOwnershipOfCommonSecuritiesIssuedByTrustIi	315000	USD
CY2020Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	253000	USD
CY2020	us-gaap	Description Of Material Affects Of Noncompliance DescriptionOfMaterialAffectsOfNoncompliance	Failure to meet minimum capital requirements can result in certain mandatory, and possibly additional discretionary actions on the part of regulators, that if undertaken, could have a direct material effect on the Bank’s assets, liabilities, and certain off-balance sheet items as calculated under regulatory practices.
CY2020Q4	us-gaap	Capital Capital	258607000	USD
CY2020Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1125
CY2020Q4	us-gaap	Capital Required For Capital Adequacy CapitalRequiredForCapitalAdequacy	183965000	USD
CY2020Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0800
CY2020Q4	fbiz	Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer CapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	241454000	USD
CY2020Q4	fbiz	Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets CapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.1050
CY2020Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	206104000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.0896
CY2020Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy TierOneRiskBasedCapitalRequiredForCapitalAdequacy	137974000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0600
CY2020Q4	fbiz	Tier One Risk Based Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer TierOneRiskBasedCapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	195463000	USD
CY2020Q4	fbiz	Tier One Risk Based Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets TierOneRiskBasedCapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.0850
CY2020Q4	us-gaap	Common Equity Tier One Capital CommonEquityTierOneCapital	196042000	USD
CY2020Q4	fbiz	Common Equity Tier One Capitalto Risk Weighted Assets CommonEquityTierOneCapitaltoRiskWeightedAssets	0.0853
CY2020Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	103480000	USD
CY2020Q4	fbiz	Common Equity Tier One Capital Requiredfor Capital Adequacyto Risk Weighted Assets CommonEquityTierOneCapitalRequiredforCapitalAdequacytoRiskWeightedAssets	0.0450
CY2020Q4	fbiz	Common Equity Tier One Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer CommonEquityTierOneCapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	160970000	USD
CY2020Q4	fbiz	Common Equity Tier One Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets CommonEquityTierOneCapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.0700
CY2020Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	206104000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.0799
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	103228000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2020Q4	fbiz	Tier One Leverage Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer TierOneLeverageCapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	103228000	USD
CY2020Q4	fbiz	Tier One Leverage Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets TierOneLeverageCapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.0400
CY2019Q4	us-gaap	Capital Capital	239029000	USD
CY2019Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1201
CY2019Q4	us-gaap	Capital Required For Capital Adequacy CapitalRequiredForCapitalAdequacy	159185000	USD
CY2019Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0800
CY2019Q4	fbiz	Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer CapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	208930000	USD
CY2019Q4	fbiz	Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets CapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.1050
CY2019Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	194456000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.0977
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy TierOneRiskBasedCapitalRequiredForCapitalAdequacy	119388000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0600
CY2019Q4	fbiz	Tier One Risk Based Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer TierOneRiskBasedCapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	169134000	USD
CY2019Q4	fbiz	Tier One Risk Based Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets TierOneRiskBasedCapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.0850
CY2019Q4	us-gaap	Common Equity Tier One Capital CommonEquityTierOneCapital	184409000	USD
CY2019Q4	fbiz	Common Equity Tier One Capitalto Risk Weighted Assets CommonEquityTierOneCapitaltoRiskWeightedAssets	0.0927
CY2019Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	89541000	USD
CY2019Q4	fbiz	Common Equity Tier One Capital Requiredfor Capital Adequacyto Risk Weighted Assets CommonEquityTierOneCapitalRequiredforCapitalAdequacytoRiskWeightedAssets	0.0450
CY2019Q4	fbiz	Common Equity Tier One Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer CommonEquityTierOneCapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	139286000	USD
CY2019Q4	fbiz	Common Equity Tier One Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets CommonEquityTierOneCapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.0700
CY2019Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	194456000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.0927
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	83950000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2019Q4	fbiz	Tier One Leverage Capital Requiredfor Capital Adequacy Plus Capital Conservation Buffer TierOneLeverageCapitalRequiredforCapitalAdequacyPlusCapitalConservationBuffer	83950000	USD
CY2019Q4	fbiz	Tier One Leverage Capital Requiredfor Capital Adequacy Plus Conservation Bufferto Risk Weighted Assets TierOneLeverageCapitalRequiredforCapitalAdequacyPlusConservationBuffertoRiskWeightedAssets	0.0400
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	206162000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	194156000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	933000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	1348000	USD
CY2020Q4	fbiz	Disallowed Servicing Assetsand Purchased Credit Card Relationships DisallowedServicingAssetsandPurchasedCreditCardRelationships	587000	USD
CY2019Q4	fbiz	Disallowed Servicing Assetsand Purchased Credit Card Relationships DisallowedServicingAssetsandPurchasedCreditCardRelationships	629000	USD
CY2020Q4	fbiz	Disallowed Goodwilland Intangibles DisallowedGoodwillandIntangibles	10466000	USD
CY2019Q4	fbiz	Disallowed Goodwilland Intangibles DisallowedGoodwillandIntangibles	10466000	USD
CY2020Q4	fbiz	Trust Preferred Securities TrustPreferredSecurities	10062000	USD
CY2019Q4	fbiz	Trust Preferred Securities TrustPreferredSecurities	10047000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	206104000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	194456000	USD
CY2020Q4	fbiz	Allowable General Valuation Allowances And Subordinated Debt AllowableGeneralValuationAllowancesAndSubordinatedDebt	52503000	USD
CY2019Q4	fbiz	Allowable General Valuation Allowances And Subordinated Debt AllowableGeneralValuationAllowancesAndSubordinatedDebt	44573000	USD
CY2020Q4	us-gaap	Capital Capital	258607000	USD
CY2019Q4	us-gaap	Capital Capital	239029000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	16978000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	23324000	USD
CY2020	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	423000	USD
CY2019	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	502000	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	16555000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	22822000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	8384464	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	8515375	shares
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.97
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.68
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	16555000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	22822000	USD
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	8384464	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	8515375	shares
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.97
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.68
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	185000	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	148757	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	176935	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	22.51
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	131621	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	21.02
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	78775	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	25.82
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	95265	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	23.64
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	56904	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	22.26
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	48207	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	20.62
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	11002	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	22.86
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	1744	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	23.67
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	187804	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	24.29
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	176935	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	22.51
CY2020Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	3200000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P2Y1M20D
CY2020	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	3967	shares
CY2020Q4	fbiz	Employee Stock Purchase Plan Number Of Shares Available For Grant EmployeeStockPurchasePlanNumberOfSharesAvailableForGrant	246033	shares
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	1871000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	1566000	USD
CY2020	fbiz	Defined Contribution Maximum Annual Matching Contribution Per Employee Percent DefinedContributionMaximumAnnualMatchingContributionPerEmployeePercent	0.03
CY2020	fbiz	Defined Contribution Maximum Annual Discretionary Contribution Per Employee Percent DefinedContributionMaximumAnnualDiscretionaryContributionPerEmployeePercent	0.06
CY2020	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent DefinedContributionPlanEmployerMatchingContributionPercent	0.03
CY2020	fbiz	Defined Contribution Plan Employer Matching Contribution DefinedContributionPlanEmployerMatchingContribution	896000	USD
CY2019	fbiz	Defined Contribution Plan Employer Matching Contribution DefinedContributionPlanEmployerMatchingContribution	783000	USD
CY2020	fbiz	Defined Contribution Plan Employer Discretionary Contribution Percent DefinedContributionPlanEmployerDiscretionaryContributionPercent	0.050
CY2020	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	1200000	USD
CY2019	fbiz	Defined Contribution Plan Employer Discretionary Contribution Percent DefinedContributionPlanEmployerDiscretionaryContributionPercent	0.041
CY2019	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	808000	USD
CY2020	us-gaap	Deferred Compensation Arrangement With Individual Compensation Expense DeferredCompensationArrangementWithIndividualCompensationExpense	193000	USD
CY2019	us-gaap	Deferred Compensation Arrangement With Individual Compensation Expense DeferredCompensationArrangementWithIndividualCompensationExpense	168000	USD
CY2020Q4	us-gaap	Deferred Compensation Cashbased Arrangements Liability Current And Noncurrent DeferredCompensationCashbasedArrangementsLiabilityCurrentAndNoncurrent	1600000	USD
CY2019Q4	us-gaap	Deferred Compensation Cashbased Arrangements Liability Current And Noncurrent DeferredCompensationCashbasedArrangementsLiabilityCurrentAndNoncurrent	1400000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	1948000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	1483000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1386000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	1988000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	3334000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	3471000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-1678000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-1979000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-329000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-317000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2007000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2296000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1327000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1175000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	7276000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	5104000	USD
CY2020Q4	fbiz	Deferred Tax Assets Tax Deferred Expense Reservesand Accruals Sba Recourse Reserve DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsSBARecourseReserve	302000	USD
CY2019Q4	fbiz	Deferred Tax Assets Tax Deferred Expense Reservesand Accruals Sba Recourse Reserve DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsSBARecourseReserve	352000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	1457000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	1335000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards State And Local DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal	482000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards State And Local DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal	526000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	1831000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	2881000	USD
CY2020Q4	fbiz	Deferred Tax Asset Non Accrual Loan Interest DeferredTaxAssetNonAccrualLoanInterest	820000	USD
CY2019Q4	fbiz	Deferred Tax Asset Non Accrual Loan Interest DeferredTaxAssetNonAccrualLoanInterest	864000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Capital Loss Carryforwards DeferredTaxAssetsCapitalLossCarryforwards	21000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Capital Loss Carryforwards DeferredTaxAssetsCapitalLossCarryforwards	22000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Unrealized Losses On Availablefor Sale Securities Gross DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross	319000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Unrealized Losses On Availablefor Sale Securities Gross DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross	464000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	356000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	531000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	12864000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	12079000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	12864000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	12079000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	4363000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	5841000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	358000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	337000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	926000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	548000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	5647000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	6726000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	7217000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	5353000	USD
CY2020	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	1864000	USD
CY2019	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	2181000	USD
CY2020	fbiz	Deferred Taxes Allocated To Other Comprehensive Income DeferredTaxesAllocatedToOtherComprehensiveIncome	143000	USD
CY2019	fbiz	Deferred Taxes Allocated To Other Comprehensive Income DeferredTaxesAllocatedToOtherComprehensiveIncome	115000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2007000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-2296000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	18305000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	24499000	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	3844000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	5145000	USD
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	837000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	1321000	USD
CY2020	fbiz	Income Tax Reconciliation Tax Exempt Income Tax Exempt Security And Loan Income Net Of Tefra Adjustments IncomeTaxReconciliationTaxExemptIncomeTaxExemptSecurityAndLoanIncomeNetOfTefraAdjustments	648000	USD
CY2019	fbiz	Income Tax Reconciliation Tax Exempt Income Tax Exempt Security And Loan Income Net Of Tefra Adjustments IncomeTaxReconciliationTaxExemptIncomeTaxExemptSecurityAndLoanIncomeNetOfTefraAdjustments	635000	USD
CY2020	fbiz	Income Tax Reconciliation Tax Exempt Income Bank Owned Life Insurance IncomeTaxReconciliationTaxExemptIncomeBankOwnedLifeInsurance	294000	USD
CY2019	fbiz	Income Tax Reconciliation Tax Exempt Income Bank Owned Life Insurance IncomeTaxReconciliationTaxExemptIncomeBankOwnedLifeInsurance	252000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	2535000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	4503000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	123000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	99000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1327000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1175000	USD
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.0725
CY2020	fbiz	Fair Value Assets Level2to Level1 Transfers Amount1 FairValueAssetsLevel2toLevel1TransfersAmount1	0	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.0480
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	0	USD
CY2020Q4	us-gaap	Significant Change In Unrecognized Tax Benefits Is Reasonably Possible Amount Of Unrecorded Benefit SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit	0	USD
CY2020	fbiz	Derivative Credit Valuation Adjustment DerivativeCreditValuationAdjustment	461000	USD
CY2020Q4	fbiz	Interest Rate Swaps Default InterestRateSwapsDefault	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Before Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax	-3000000.0	USD
CY2020	us-gaap	Derivative Instruments Gain Loss Recognized In Income Ineffective Portion And Amount Excluded From Effectiveness Testing Net DerivativeInstrumentsGainLossRecognizedInIncomeIneffectivePortionAndAmountExcludedFromEffectivenessTestingNet	0	USD
CY2020Q4	fbiz	Accrued Credit Losses For Financial Instruments With Off Balance Sheet Risk AccruedCreditLossesForFinancialInstrumentsWithOffBalanceSheetRisk	0	USD
CY2019Q4	fbiz	Accrued Credit Losses For Financial Instruments With Off Balance Sheet Risk AccruedCreditLossesForFinancialInstrumentsWithOffBalanceSheetRisk	0	USD
CY2020Q4	fbiz	Sba Loans Probabilityof Future Losses SBALoansProbabilityofFutureLosses	723000	USD
CY2019Q4	fbiz	Sba Loans Probabilityof Future Losses SBALoansProbabilityofFutureLosses	1300000	USD
CY2019Q4	fbiz	Sba Recourse Reserve SBARecourseReserve	1345000	USD
CY2018Q4	fbiz	Sba Recourse Reserve SBARecourseReserve	2956000	USD
CY2020	fbiz	Sba Recourse Provision SBARecourseProvision	-278000	USD
CY2019	fbiz	Sba Recourse Provision SBARecourseProvision	188000	USD
CY2020	fbiz	Sba Loan Charge Offs Net SBALoanChargeOffsNet	-344000	USD
CY2019	fbiz	Sba Loan Charge Offs Net SBALoanChargeOffsNet	-1799000	USD
CY2020Q4	fbiz	Sba Recourse Reserve SBARecourseReserve	723000	USD
CY2019Q4	fbiz	Sba Recourse Reserve SBARecourseReserve	1345000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3	0	USD
CY2019	fbiz	Fair Value Liabilities Level2to Level1 Transfers Amount1 FairValueLiabilitiesLevel2toLevel1TransfersAmount1	0	USD
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CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Liability Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3	0	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3	0	USD
CY2019	fbiz	Fair Value Liabilities Level1to Level2 Transfers Amount1 FairValueLiabilitiesLevel1toLevel2TransfersAmount1	0	USD
CY2020	fbiz	Fair Value Liabilities Level2to Level1 Transfers Amount1 FairValueLiabilitiesLevel2toLevel1TransfersAmount1	0	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Liability Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3	0	USD
CY2020	fbiz	Fair Value Liabilities Level1to Level2 Transfers Amount1 FairValueLiabilitiesLevel1toLevel2TransfersAmount1	0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Liability Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	26374000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	27333000	USD
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CY2020Q4	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	56909000	USD
CY2020Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	183925000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	183925000	USD
CY2020Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	8695000	USD
CY2020Q4	us-gaap	Loans Held For Sale Fair Value Disclosure LoansHeldForSaleFairValueDisclosure	9478000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	2117449000	USD
CY2020Q4	us-gaap	Loans Receivable Fair Value Disclosure LoansReceivableFairValueDisclosure	2121107000	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	13578000	USD
CY2020Q4	us-gaap	Interest Receivable InterestReceivable	8564000	USD
CY2020Q4	fbiz	Accrued Interest Receivable Fair Value Disclosure AccruedInterestReceivableFairValueDisclosure	8564000	USD
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CY2020Q4	us-gaap	Deposits Fair Value Disclosure DepositsFairValueDisclosure	1856910000	USD
CY2020Q4	fbiz	Federal Home Loan Bank And Other Borrowings FederalHomeLoanBankAndOtherBorrowings	419167000	USD
CY2020Q4	fbiz	Federal Home Loan Bank And Other Borrowings Fair Value Disclosure FederalHomeLoanBankAndOtherBorrowingsFairValueDisclosure	429347000	USD
CY2020Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	10062000	USD
CY2020Q4	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	9986000	USD
CY2020Q4	us-gaap	Interest Payable Current And Noncurrent InterestPayableCurrentAndNoncurrent	1578000	USD
CY2020Q4	us-gaap	Accrued Liabilities Fair Value Disclosure AccruedLiabilitiesFairValueDisclosure	1578000	USD
CY2020Q4	us-gaap	Letters Of Credit Outstanding Amount LettersOfCreditOutstandingAmount	75000	USD
CY2020Q4	fbiz	Standby Letters Of Credit Fair Value Disclosure StandbyLettersOfCreditFairValueDisclosure	75000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	67102000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents Fair Value Disclosure CashAndCashEquivalentsFairValueDisclosure	67102000	USD
CY2019Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	173133000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	173133000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	32700000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	33188000	USD
CY2019Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	5205000	USD
CY2019Q4	us-gaap	Loans Held For Sale Fair Value Disclosure LoansHeldForSaleFairValueDisclosure	5673000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	1695115000	USD
CY2019Q4	us-gaap	Loans Receivable Fair Value Disclosure LoansReceivableFairValueDisclosure	1706201000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Stock FederalHomeLoanBankStock	7953000	USD
CY2019Q4	us-gaap	Interest Receivable InterestReceivable	5760000	USD
CY2019Q4	fbiz	Accrued Interest Receivable Fair Value Disclosure AccruedInterestReceivableFairValueDisclosure	5760000	USD
CY2019Q4	us-gaap	Deposits Deposits	1530379000	USD
CY2019Q4	us-gaap	Deposits Fair Value Disclosure DepositsFairValueDisclosure	1532517000	USD
CY2019Q4	fbiz	Federal Home Loan Bank And Other Borrowings FederalHomeLoanBankAndOtherBorrowings	319382000	USD
CY2019Q4	fbiz	Federal Home Loan Bank And Other Borrowings Fair Value Disclosure FederalHomeLoanBankAndOtherBorrowingsFairValueDisclosure	319507000	USD
CY2019Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	10047000	USD
CY2019Q4	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	9970000	USD
CY2019Q4	us-gaap	Interest Payable Current And Noncurrent InterestPayableCurrentAndNoncurrent	2882000	USD
CY2019Q4	us-gaap	Accrued Liabilities Fair Value Disclosure AccruedLiabilitiesFairValueDisclosure	2882000	USD
CY2019Q4	us-gaap	Letters Of Credit Outstanding Amount LettersOfCreditOutstandingAmount	63000	USD
CY2019Q4	fbiz	Standby Letters Of Credit Fair Value Disclosure StandbyLettersOfCreditFairValueDisclosure	63000	USD
CY2020	fbiz	Proceeds From Purchases Of Employee Stock Purchase Plan Shares ProceedsFromPurchasesOfEmployeeStockPurchasePlanShares	66000	USD
CY2019	fbiz	Proceeds From Purchases Of Employee Stock Purchase Plan Shares ProceedsFromPurchasesOfEmployeeStockPurchasePlanShares	0	USD
CY2020Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	25770000	USD
CY2020Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	22276000	USD
CY2020Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	22761000	USD
CY2020Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	23372000	USD
CY2019Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	25679000	USD
CY2020Q4	us-gaap	Interest Expense InterestExpense	3258000	USD
CY2019Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	25613000	USD
CY2019Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	25438000	USD
CY2019Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	25309000	USD
CY2020Q3	us-gaap	Interest Expense InterestExpense	3655000	USD
CY2020Q2	us-gaap	Interest Expense InterestExpense	3873000	USD
CY2020Q1	us-gaap	Interest Expense InterestExpense	6322000	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	7139000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	8662000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	8457000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	7925000	USD
CY2020Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	22512000	USD
CY2020Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	18621000	USD
CY2020Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	18888000	USD
CY2020Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	17050000	USD
CY2019Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	18474000	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	16776000	USD
CY2019Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	16852000	USD
CY2019Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	17754000	USD
CY2020Q4	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4322000	USD
CY2020Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3835000	USD
CY2020Q2	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5469000	USD
CY2020Q1	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3182000	USD
CY2019Q4	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1472000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1349000	USD
CY2019Q2	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	-784000	USD
CY2019Q1	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	49000	USD
CY2020Q4	us-gaap	Noninterest Income NoninterestIncome	6799000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	7408000	USD
CY2020Q2	us-gaap	Noninterest Income NoninterestIncome	6319000	USD
CY2020Q1	us-gaap	Noninterest Income NoninterestIncome	6414000	USD
CY2019Q2	us-gaap	Noninterest Income NoninterestIncome	5805000	USD
CY2019Q1	us-gaap	Noninterest Income NoninterestIncome	4638000	USD
CY2019Q4	us-gaap	Noninterest Income NoninterestIncome	7189000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	5792000	USD
CY2020Q4	us-gaap	Noninterest Expense NoninterestExpense	17651000	USD
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	16758000	USD
CY2020Q2	us-gaap	Noninterest Expense NoninterestExpense	18343000	USD
CY2020Q1	us-gaap	Noninterest Expense NoninterestExpense	16146000	USD
CY2019Q4	us-gaap	Noninterest Expense NoninterestExpense	16773000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	14716000	USD
CY2019Q2	us-gaap	Noninterest Expense NoninterestExpense	17464000	USD
CY2019Q1	us-gaap	Noninterest Expense NoninterestExpense	17742000	USD
CY2020Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	7338000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	5436000	USD
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	1395000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	4136000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	7418000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	6503000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	5977000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	4601000	USD
CY2020Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1254000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1143000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-1928000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	858000	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1650000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1418000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-595000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-1298000	USD
CY2020Q4	us-gaap	Net Income Loss NetIncomeLoss	6084000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	4293000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	3323000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	3278000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	5768000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	5085000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	6572000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	5899000	USD
CY2020Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.71
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.50
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.38
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.38
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.67
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.59
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.75
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.67
CY2020Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.71
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.50
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.38
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.38
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.67
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.59
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.75
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.67
CY2020Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.165
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.165
CY2020Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.165
CY2020Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.165
CY2019Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.15
CY2019Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.15
CY2019Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.15
CY2019Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.15

Files In Submission

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$FBIZ
FIRST BUSINESS FINANCIAL SERVICES, INC. Stock $fbiz

2019 Q4 Form 10-K Financial Statement

#000152195121000028 Filed on February 24, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FBIZ FIRST BUSINESS FINANCIAL SERVICES, INC. Stock $fbiz

2019 Q4 Form 10-K Financial Statement

#000152195121000028 Filed on February 24, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FBIZ
FIRST BUSINESS FINANCIAL SERVICES, INC. Stock $fbiz