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Regulatory Capital (Regulatory Capital Ratios) (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016
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Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital (to risk-weighted assets) | $ 209,495 | $ 204,117
Total capital to risk-weighted assets | 11.91% | 11.74%
Total capital, Minimum Required for Capital Adequacy Purposes | $ 140,737 | $ 139,101
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 8.00% | 8.00%
Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 162,727 | $ 149,968
Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 9.25% | 8.625%
Tier 1 capital (to risk-weighted assets) | $ 165,873 | $ 160,964
Tier 1 capital to risk-weighted assets | 9.43% | 9.26%
Tier 1 capital, Minimum Required for Capital Adequacy Purposes | $ 105,553 | $ 104,326
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 6.00% | 6.00%
Tier One Risk Based Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 127,543 | $ 115,193
Tier One Risk Based Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 7.25% | 6.625%
Common equity tier 1 capital | $ 155,858 | $ 150,960
Common equity tier 1 capital to risk-weighted assets | 8.86% | 8.68%
Common equity tier 1 capital, Minimum Required for Capital Adequacy Purposes | $ 79,164 | $ 78,244
Common equity tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 4.50% | 4.50%
Common Equity Tier One Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 101,155 | $ 89,111
Common Equity Tier One Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 5.75% | 5.125%
Tier 1 leverage capital (to adjusted assets) | $ 165,873 | $ 160,964
Tier 1 leverage capital to average assets | 9.39% | 9.07%
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes | $ 70,654 | $ 70,985
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes | 4.00% | 4.00%
Tier One Leverage Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 70,654 | $ 70,985
Tier One Leverage Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 4.00% | 4.00%
First Business Bank |  |
Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital (to risk-weighted assets) | $ 205,877 | $ 147,811
Total capital to risk-weighted assets | 11.75% | 11.55%
Total capital, Minimum Required for Capital Adequacy Purposes | $ 140,132 | $ 102,362
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 8.00% | 8.00%
Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 162,027 | $ 110,360
Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 9.25% | 8.625%
Total capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | $ 175,164 | $ 127,953
Total capital to risk-weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 10.00% | 10.00%
Tier 1 capital (to risk-weighted assets) | $ 185,954 | $ 134,208
Tier 1 capital to risk-weighted assets | 10.62% | 10.49%
Tier 1 capital, Minimum Required for Capital Adequacy Purposes | $ 105,099 | $ 76,772
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 6.00% | 6.00%
Tier One Risk Based Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 126,994 | $ 84,769
Tier One Risk Based Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 7.25% | 6.625%
Tier 1 capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | $ 140,132 | $ 102,362
Tier 1 capital to risk weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 8.00% | 8.00%
Common equity tier 1 capital | $ 185,954 | $ 134,208
Common equity tier 1 capital to risk-weighted assets | 10.62% | 10.49%
Common equity tier 1 capital, Minimum Required for Capital Adequacy Purposes | $ 78,824 | $ 57,579
Common equity tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes | 4.50% | 4.50%
Common Equity Tier One Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 100,720 | $ 65,576
Common Equity Tier One Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 5.75% | 5.125%
Common equity tier 1 capital, Minimum Required to Be Well Capitalized Under Prompt Corrective Action Requirements | $ 113,857 | $ 83,170
Common equity tier 1 capital to risk-weighted assets, Minimum Required to Be Well Capitalized Under Prompt Corrective Action Requirements | 6.50% | 6.50%
Tier 1 leverage capital (to adjusted assets) | $ 185,954 | $ 134,208
Tier 1 leverage capital to average assets | 10.56% | 10.40%
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes | $ 70,409 | $ 51,600
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes | 4.00% | 4.00%
Tier One Leverage Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 70,409 | $ 51,600
Tier One Leverage Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 4.00% | 4.00%
Tier 1 leverage capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | $ 88,011 | $ 64,500
Tier 1 leverage capital to average assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 5.00% | 5.00%
First Business Bank - Milwaukee |  |
Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital (to risk-weighted assets) |  | $ 24,347
Total capital to risk-weighted assets |  | 11.02%
Total capital, Minimum Required for Capital Adequacy Purposes |  | $ 17,680
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes |  | 8.00%
Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 19,062
Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 8.625%
Total capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 22,101
Total capital to risk-weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | 10.00%
Tier 1 capital (to risk-weighted assets) |  | $ 22,323
Tier 1 capital to risk-weighted assets |  | 10.10%
Tier 1 capital, Minimum Required for Capital Adequacy Purposes |  | $ 13,260
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes |  | 6.00%
Tier One Risk Based Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 14,642
Tier One Risk Based Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 6.625%
Tier 1 capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 17,680
Tier 1 capital to risk weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | 8.00%
Common equity tier 1 capital |  | $ 22,323
Common equity tier 1 capital to risk-weighted assets |  | 10.10%
Common equity tier 1 capital, Minimum Required for Capital Adequacy Purposes |  | $ 9,945
Common equity tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes |  | 4.50%
Common Equity Tier One Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 11,327
Common Equity Tier One Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 5.125%
Common equity tier 1 capital, Minimum Required to Be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 14,365
Common equity tier 1 capital to risk-weighted assets, Minimum Required to Be Well Capitalized Under Prompt Corrective Action Requirements |  | 6.50%
Tier 1 leverage capital (to adjusted assets) |  | $ 22,323
Tier 1 leverage capital to average assets |  | 9.15%
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes |  | $ 9,758
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes |  | 4.00%
Tier One Leverage Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 9,758
Tier One Leverage Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 4.00%
Tier 1 leverage capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 12,198
Tier 1 leverage capital to average assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | 5.00%
Alterra Bank |  |
Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total capital (to risk-weighted assets) |  | $ 31,699
Total capital to risk-weighted assets |  | 13.27%
Total capital, Minimum Required for Capital Adequacy Purposes |  | $ 19,106
Total capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes |  | 8.00%
Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 20,599
Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 8.625%
Total capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 23,882
Total capital to risk-weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | 10.00%
Tier 1 capital (to risk-weighted assets) |  | $ 28,685
Tier 1 capital to risk-weighted assets |  | 12.01%
Tier 1 capital, Minimum Required for Capital Adequacy Purposes |  | $ 14,329
Tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes |  | 6.00%
Tier One Risk Based Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 15,822
Tier One Risk Based Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 6.625%
Tier 1 capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 19,106
Tier 1 capital to risk weighted assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | 8.00%
Common equity tier 1 capital |  | $ 28,685
Common equity tier 1 capital to risk-weighted assets |  | 12.01%
Common equity tier 1 capital, Minimum Required for Capital Adequacy Purposes |  | $ 10,747
Common equity tier 1 capital to risk-weighted assets, Minimum Required for Capital Adequacy Purposes |  | 4.50%
Common Equity Tier One Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 12,240
Common Equity Tier One Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 5.125%
Common equity tier 1 capital, Minimum Required to Be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 15,524
Common equity tier 1 capital to risk-weighted assets, Minimum Required to Be Well Capitalized Under Prompt Corrective Action Requirements |  | 6.50%
Tier 1 leverage capital (to adjusted assets) |  | $ 28,685
Tier 1 leverage capital to average assets |  | 10.58%
Tier 1 leverage capital, Minimum Required for Capital Adequacy Purposes |  | $ 10,842
Tier 1 leverage capital to average assets, Minimum Required for Capital Adequacy Purposes |  | 4.00%
Tier One Leverage Capital Required for Capital Adequacy Plus Capital Conservation Buffer |  | $ 10,842
Tier One Leverage Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets |  | 4.00%
Tier 1 leverage capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | $ 13,552
Tier 1 leverage capital to average assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements |  | 5.00%

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- Definition The amount of total capital as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826 Reference 3: 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=84167132&loc=d3e65071-112826 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998 + Details
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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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 Reference 2: 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=84167132&loc=d3e65071-112826 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=84167132&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=84167132&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=84167132&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=84167132&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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 Reference 2: 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=84167132&loc=d3e65071-112826 + Details
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- Definition The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average 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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 Reference 2: 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=84167132&loc=d3e65071-112826 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=84167132&loc=SL5958570-112826 + 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=84167132&loc=SL5958568-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in 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=84167132&loc=SL5958568-112826 + Details
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- Definition Tier 1 Risk Based Capital 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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 Reference 2: 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=84167132&loc=d3e65071-112826 + Details
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- Definition The minimum amount of Tier 1 Risk Based 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=84167132&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=84167132&loc=SL5958568-112826 + Details
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- Definition The minimum Tier One Capital Ratio (Tier one 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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 Reference 2: 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=84167132&loc=SL5958570-112826 Reference 3: 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=84167132&loc=d3e65071-112826 + Details
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- Definition The amount of Tier 1 Risk Based 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=84167132&loc=SL5958568-112826 + Details
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- Definition Tier 1 capital divided by risk weighted assets as defined by regulations. + 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=84167132&loc=SL5958568-112826 Reference 2: 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=84167132&loc=d3e65071-112826 + Details
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