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Regulatory Capital (Regulatory Capital Ratios) (Details) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital | $ 177,594 us-gaap_Capital | $ 173,263 us-gaap_Capital
Total capital to risk-weighted assets | 11.40%us-gaap_CapitalToRiskWeightedAssets | 12.13%us-gaap_CapitalToRiskWeightedAssets
Total capital, Minimum Required for Capital Adequacy Purposes | 124,677 us-gaap_CapitalRequiredForCapitalAdequacy | 114,253 us-gaap_CapitalRequiredForCapitalAdequacy
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Tier 1 capital | 139,974 us-gaap_TierOneRiskBasedCapital | 136,008 us-gaap_TierOneRiskBasedCapital
Tier 1 Capital to Risk-Weighted Assets | 8.98%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets | 9.52%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Tier 1 Capital, Minimum Required for Capital Adequacy Purposes | 93,508 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy | 57,127 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Common Equity Tier One Capital | 129,974 fbiz_CommonEquityTierOneCapital |
Common Equity Tier One Capital to Risk-Weighted Assets | 8.34%fbiz_CommonEquityTierOneCapitaltoRiskWeightedAssets |
Common Equity Tier One Capital Required for Capital Adequacy | 70,131 fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacy |
Common Equity Tier One Capital Required for Capital Adequacy to Risk-Weighted Assets | 4.50%fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacytoRiskWeightedAssets |
Tier 1 capital | 139,974 us-gaap_TierOneLeverageCapital | 136,008 us-gaap_TierOneLeverageCapital
Tier 1 leverage capital to average assets | 8.42%us-gaap_TierOneLeverageCapitalToAverageAssets | 8.71%us-gaap_TierOneLeverageCapitalToAverageAssets
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes | 5,199 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy | 62,490 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
First Business Bank |  |
Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital | 133,667 us-gaap_Capital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 131,411 us-gaap_Capital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Total capital to risk-weighted assets | 11.47%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 12.19%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Total capital, Minimum Required for Capital Adequacy Purposes | 93,216 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 86,272 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Total capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 116,544 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 107,841 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Total capital to risk-weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 capital | 121,166 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 118,907 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 Capital to Risk-Weighted Assets | 10.40%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 11.03%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 Capital, Minimum Required for Capital Adequacy Purposes | 69,912 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 43,136 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 93,235 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 64,704 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 capital to risk weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 8.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Common Equity Tier One Capital | 121,166 fbiz_CommonEquityTierOneCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember |
Common Equity Tier One Capital to Risk-Weighted Assets | 10.40%fbiz_CommonEquityTierOneCapitaltoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember |
Common Equity Tier One Capital Required for Capital Adequacy | 52,434 fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember |
Common Equity Tier One Capital Required for Capital Adequacy to Risk-Weighted Assets | 4.50%fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacytoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember |
Common Equity Tier One Capital to be Well Capitalized | 101,318 fbiz_CommonEquityTierOneCapitaltobeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember |
Common Equity Tier One Capital Required to be Well Capitalized to Risk-Weighted Assets | 6.50%fbiz_CommonEquityTierOneCapitalRequiredtobeWellCapitalizedtoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember |
Tier 1 capital | 121,166 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 118,907 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 leverage capital to average assets | 10.33%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 10.13%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes | 4,847 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 46,960 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 leverage capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 6,061 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 58,700 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
Tier 1 leverage capital to average assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMember
First Business Bank - Milwaukee |  |
Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital | 19,215 us-gaap_Capital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 19,128 us-gaap_Capital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Total capital to risk-weighted assets | 12.17%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 12.47%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Total capital, Minimum Required for Capital Adequacy Purposes | 12,626 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 12,274 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Total capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 15,783 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 15,343 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Total capital to risk-weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 capital | 17,721 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 17,641 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 Capital to Risk-Weighted Assets | 11.23%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 11.50%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 Capital, Minimum Required for Capital Adequacy Purposes | 9,470 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 6,137 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 12,626 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 9,206 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 capital to risk weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 8.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Common Equity Tier One Capital | 17,721 fbiz_CommonEquityTierOneCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember |
Common Equity Tier One Capital to Risk-Weighted Assets | 11.23%fbiz_CommonEquityTierOneCapitaltoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember |
Common Equity Tier One Capital Required for Capital Adequacy | 7,102 fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember |
Common Equity Tier One Capital Required for Capital Adequacy to Risk-Weighted Assets | 4.50%fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacytoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember |
Common Equity Tier One Capital to be Well Capitalized | 75,753 fbiz_CommonEquityTierOneCapitaltobeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember |
Common Equity Tier One Capital Required to be Well Capitalized to Risk-Weighted Assets | 6.50%fbiz_CommonEquityTierOneCapitalRequiredtobeWellCapitalizedtoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember |
Tier 1 capital | 17,721 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 17,641 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 leverage capital to average assets | 7.56%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 7.90%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes | 709 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 8,935 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 leverage capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 886 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 11,169 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Tier 1 leverage capital to average assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = fbiz_FirstBusinessBankMilwaukeeMember
Alterra Bank [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital | 26,346 us-gaap_Capital / dei_LegalEntityAxis = fbiz_AlterraBankMember | 22,657 us-gaap_Capital / dei_LegalEntityAxis = fbiz_AlterraBankMember
Total capital to risk-weighted assets | 11.05%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 10.90%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Total capital, Minimum Required for Capital Adequacy Purposes | 19,072 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember | 16,628 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Total capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 23,841 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember | 20,785 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember
Total capital to risk-weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 capital | 25,647 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = fbiz_AlterraBankMember | 22,320 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 Capital to Risk-Weighted Assets | 10.76%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 10.74%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 Capital, Minimum Required for Capital Adequacy Purposes | 14,304 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember | 8,314 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 19,073 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember | 12,471 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 capital to risk weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 8.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Common Equity Tier One Capital | 25,647 fbiz_CommonEquityTierOneCapital / dei_LegalEntityAxis = fbiz_AlterraBankMember |
Common Equity Tier One Capital to Risk-Weighted Assets | 10.76%fbiz_CommonEquityTierOneCapitaltoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember |
Common Equity Tier One Capital Required for Capital Adequacy | 10,728 fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember |
Common Equity Tier One Capital Required for Capital Adequacy to Risk-Weighted Assets | 4.50%fbiz_CommonEquityTierOneCapitalRequiredforCapitalAdequacytoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember |
Common Equity Tier One Capital to be Well Capitalized | 10,259 fbiz_CommonEquityTierOneCapitaltobeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember |
Common Equity Tier One Capital Required to be Well Capitalized to Risk-Weighted Assets | 6.50%fbiz_CommonEquityTierOneCapitalRequiredtobeWellCapitalizedtoRiskWeightedAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember |
Tier 1 capital | 25,647 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = fbiz_AlterraBankMember | 22,320 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 leverage capital to average assets | 9.68%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 9.01%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes | 1,026 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember | 9,910 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 leverage capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | $ 1,270 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember | $ 12,388 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = fbiz_AlterraBankMember
Tier 1 leverage capital to average assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = fbiz_AlterraBankMember

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- Definition The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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- Definition The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Total Capital divided by risk weighted assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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