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Loan and Lease Receivables, Impaired Loans and Leases and Allowance for Loan and Lease Losses (Impaired Loans and Leases) (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 | Dec. 31, 2014
Recorded investment |  |  |  |
With no impairment reserve recorded | $ 10,475 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment |  | $ 11,270 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment |
With impairment reserve recorded | 849 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment |  | 525 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment |
Total | 11,324 us-gaap_ImpairedFinancingReceivableRecordedInvestment |  | 11,795 us-gaap_ImpairedFinancingReceivableRecordedInvestment |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 15,112 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance |  | 15,623 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance |
With impairment reserve recorded | 889 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance |  | 565 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance |
Total | 16,001 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance |  | 16,188 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance |
Impairment reserve |  |  |  |
Impairment reserve | 391 us-gaap_ImpairedFinancingReceivableRelatedAllowance |  | 290 us-gaap_ImpairedFinancingReceivableRelatedAllowance |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 11,442 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment | [1] | 13,926 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment | [1]
With impairment reserve recorded | 519 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment | [1] | 548 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment | [1]
Total | 11,961 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment | [1] | 14,474 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 167 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome |  | 843 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome |
With impairment reserve recorded | 12 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome |  | 27 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome |
Foregone interest income | 179 fbiz_ImpairedFinancingReceivableForegoneInterestIncome |  | 870 fbiz_ImpairedFinancingReceivableForegoneInterestIncome |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 1 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod |  | 740 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod |
Total | 1 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod |  | 740 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 166 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome |  | 103 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome |
With impairment reserve recorded | 12 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome |  | 27 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome |
Total | 178 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome |  | 130 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome |
Commercial real estate — owner occupied |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 568 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 577 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Total | 568 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 577 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 568 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 577 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Total | 568 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 577 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Impairment reserve |  |  |  |
Impairment reserve | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 573 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember | [1] | 484 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember | [1]
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember | [1] | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember | [1]
Total | 573 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember | [1] | 484 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 6 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 30 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Foregone interest income | 6 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 30 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 79 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 79 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 6 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | (49)fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Total | 6 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |  | (49)fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableOwnerOccupiedMember |
Commercial real estate — non-owner occupied |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 919 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 921 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
With impairment reserve recorded | 48 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 49 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Total | 967 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 970 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 919 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 921 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
With impairment reserve recorded | 88 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 89 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Total | 1,007 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 1,010 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Impairment reserve |  |  |  |
Impairment reserve | 48 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 49 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 921 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember | [1] | 349 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember | [1]
With impairment reserve recorded | 48 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember | [1] | 52 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember | [1]
Total | 969 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember | [1] | 401 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 3 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 22 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
With impairment reserve recorded | 1 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 4 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Foregone interest income | 4 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 26 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 3 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 22 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
With impairment reserve recorded | 1 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 4 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Total | 4 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |  | 26 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableNonOwnerOccupiedMember |
Construction and land development |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 5,068 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 5,157 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Total | 5,068 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 5,157 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 7,738 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 7,828 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Total | 7,738 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 7,828 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Impairment reserve |  |  |  |
Impairment reserve | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 5,135 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember | [1] | 5,285 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember | [1]
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember | [1] | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember | [1]
Total | 5,135 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember | [1] | 5,285 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 37 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 155 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Foregone interest income | 37 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 155 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 37 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 155 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Total | 37 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |  | 155 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableConstructionAndLandDevelopmentMember |
Multi-family |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 14 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 17 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Total | 14 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 17 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 380 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 384 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Total | 380 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 384 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Impairment reserve |  |  |  |
Impairment reserve | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 15 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember | [1] | 24 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember | [1]
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember | [1] | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember | [1]
Total | 15 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember | [1] | 24 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 13 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 53 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Foregone interest income | 13 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 53 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 13 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 53 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
Total | 13 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |  | 53 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivableMultiFamilyMember |
1-4 family |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 1,351 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 1,181 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
With impairment reserve recorded | 427 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 390 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Total | 1,778 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 1,571 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 1,361 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 1,218 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
With impairment reserve recorded | 427 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 390 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Total | 1,788 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 1,608 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Impairment reserve |  |  |  |
Impairment reserve | 159 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 155 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 1,459 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember | [1] | 380 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember | [1]
With impairment reserve recorded | 386 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember | [1] | 405 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember | [1]
Total | 1,845 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember | [1] | 785 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 10 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 15 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
With impairment reserve recorded | 5 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 18 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Foregone interest income | 15 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 33 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 12 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 12 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 10 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 3 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
With impairment reserve recorded | 5 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 18 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Total | 15 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |  | 21 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialRealEstateLoansReceivable14FamilyMember |
Commercial and industrial |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 1,482 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 2,316 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
With impairment reserve recorded | 322 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 33 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Total | 1,804 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 2,349 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 2,406 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 2,926 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
With impairment reserve recorded | 322 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 33 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Total | 2,728 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 2,959 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Impairment reserve |  |  |  |
Impairment reserve | 132 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 33 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 2,252 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember | [1] | 6,141 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember | [1]
With impairment reserve recorded | 33 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember | [1] | 34 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember | [1]
Total | 2,285 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember | [1] | 6,175 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 74 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 463 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
With impairment reserve recorded | 5 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Foregone interest income | 79 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 463 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 1 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 649 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Total | 1 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 649 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 73 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | (186)fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
With impairment reserve recorded | 5 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Total | 78 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |  | (186)fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_CommercialAndIndustrialLoansReceivableMember |
Direct financing leases, net |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Total | 0 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Total | 0 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Impairment reserve |  |  |  |
Impairment reserve | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember | [1] | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember | [1]
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember | [1] | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember | [1]
Total | 0 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember | [1] | 0 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Foregone interest income | 0 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Total | 0 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_FinanceLeasesFinancingReceivableMember |
Home equity and second mortgages |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 371 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 380 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
With impairment reserve recorded | 52 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 53 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Total | 423 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 433 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 371 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 380 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
With impairment reserve recorded | 52 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 53 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Total | 423 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 433 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Impairment reserve |  |  |  |
Impairment reserve | 52 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 53 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 375 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember | [1] | 495 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember | [1]
With impairment reserve recorded | 52 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember | [1] | 57 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember | [1]
Total | 427 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember | [1] | 552 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 4 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 18 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
With impairment reserve recorded | 1 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 5 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Foregone interest income | 5 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 23 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 4 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 18 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
With impairment reserve recorded | 1 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 5 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Total | 5 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |  | 23 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_HomeEquityLoansAndSecondMortageLoansReceivableMember |
Other |  |  |  |
Recorded investment |  |  |  |
With no impairment reserve recorded | 702 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 721 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Total | 702 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 721 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Unpaid principal balance |  |  |  |
With no impairment reserve recorded | 1,369 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 1,389 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Total | 1,369 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 1,389 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Impairment reserve |  |  |  |
Impairment reserve | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Average recorded investment(1) |  |  |  |
With no impairment reserve recorded | 712 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember | [1] | 768 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember | [1]
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember | [1] | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember | [1]
Total | 712 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember | [1] | 768 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember | [1]
Foregone interest income |  |  |  |
With no impairment reserve recorded | 20 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 87 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Foregone interest income | 20 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 87 fbiz_ImpairedFinancingReceivableForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Interest income recognized |  |  |  |
With no impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
With impairment reserve recorded | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Total | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 us-gaap_ImpairedFinancingReceivableInterestIncomeCashBasisMethod / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Net foregone interest income |  |  |  |
With no impairment reserve recorded | 20 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 87 fbiz_ImpairedFinancingReceivableWithNoRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
With impairment reserve recorded | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | 0 fbiz_ImpairedFinancingReceivableWithRelatedAllowanceNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
Total | $ 20 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |  | $ 87 fbiz_ImpairedFinancingReceivableNetForegoneInterestIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fbiz_OtherLoansReceivableMember |
[1] | (1)Average recorded investment is calculated primarily using daily average balances.

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