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Stockholders' Equity and Regulatory Capital (Regulatory Capital Ratios) (Details) $ in Thousands | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($)
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Compliance with Regulatory Capital Requirements under Banking Regulations |  |
Total Capital | $ 375,440 | $ 323,893
Total Capital to Risk-Weighted Assets | 0.1119 | 0.1126
Total Capital, Minimum Required for Capital Adequacy Purposes | $ 268,500 | $ 230,180
Total Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes | 0.0800 | 0.0800
Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 352,406 | $ 302,111
Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 10.50% | 10.50%
Tier 1 capital | $ 293,338 | $ 264,843
Tier 1 Capital to Risk-Weighted Assets | 0.0874 | 0.0920
Tier 1 Capital, Minimum Required for Capital Adequacy Purposes | $ 201,375 | $ 172,635
Tier 1 Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes | 0.0600 | 0.0600
Tier One Risk Based Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 285,281 | $ 244,566
Tier One Risk Based Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 8.50% | 8.50%
Common Equity Tier One Capital | $ 281,346 | $ 252,851
Common Equity Tier One Capital to Risk-Weighted Assets | 8.38% | 8.79%
Common Equity Tier One Capital Required for Capital Adequacy | $ 151,031 | $ 129,476
Common Equity Tier One Capital Required for Capital Adequacy to Risk-Weighted Assets | 4.50% | 4.50%
Common Equity Tier One Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 234,937 | $ 201,407
Common Equity Tier One Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 7.00% | 7.00%
Tier 1 Capital | $ 293,338 | $ 264,843
Tier 1 Capital to Average Assets | 0.0843 | 0.0917
Tier 1 Leverage Capital, Minimum Required for Capital Adequacy Purposes | $ 139,145 | $ 115,464
Tier 1 Leverage Capital to Average Assets, Minimum Required for Capital Adequacy Purposes | 0.0400 | 0.0400
Tier One Leverage Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 139,145 | $ 115,464
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 | $ 376,310 | $ 323,021
Total Capital to Risk-Weighted Assets | 0.1121 | 0.1122
Total Capital, Minimum Required for Capital Adequacy Purposes | $ 268,595 | $ 230,367
Total Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes | 0.0800 | 0.0800
Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 352,531 | $ 302,357
Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 10.50% | 10.50%
Total Capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | $ 335,744 | $ 287,959
Total Capital to Risk-Weighted Assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 0.1000 | 0.1000
Tier 1 capital | $ 343,604 | $ 298,312
Tier 1 Capital to Risk-Weighted Assets | 0.1023 | 0.1036
Tier 1 Capital, Minimum Required for Capital Adequacy Purposes | $ 201,446 | $ 172,775
Tier 1 Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes | 0.0600 | 0.0600
Tier One Risk Based Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 285,382 | $ 244,765
Tier One Risk Based Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 8.50% | 8.50%
Tier 1 Capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | $ 268,595 | $ 230,367
Tier 1 Capital, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 0.0800 | 0.0800
Common Equity Tier One Capital | $ 343,604 | $ 298,312
Common Equity Tier One Capital to Risk-Weighted Assets | 10.23% | 10.36%
Common Equity Tier One Capital Required for Capital Adequacy | $ 151,085 | $ 129,581
Common Equity Tier One Capital Required for Capital Adequacy to Risk-Weighted Assets | 4.50% | 4.50%
Common Equity Tier One Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 235,021 | $ 201,571
Common Equity Tier One Capital Required for Capital Adequacy Plus Conservation Buffer to Risk Weighted Assets | 7.00% | 7.00%
Common Equity Tier One Capital to be Well Capitalized | $ 218,233 | $ 187,173
Common Equity Tier One Capital Required to be Well Capitalized to Risk-Weighted Assets | 6.50% | 6.50%
Tier 1 Capital | $ 343,604 | $ 298,312
Tier 1 Capital to Average Assets | 0.0987 | 0.1034
Tier 1 Leverage Capital, Minimum Required for Capital Adequacy Purposes | $ 139,262 | $ 115,402
Tier 1 Leverage Capital to Average Assets, Minimum Required for Capital Adequacy Purposes | 0.0400 | 0.0400
Tier One Leverage Capital Required for Capital Adequacy Plus Capital Conservation Buffer | $ 139,262 | $ 115,402
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 | $ 174,077 | $ 144,252
Tier 1 Leverage Capital to Average Assets, Minimum Required to be Well Capitalized Under Prompt Corrective Action Requirements | 0.0500 | 0.0500

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