| Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] | 
    
     
      
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         Actual   | 
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         For Capital Adequacy  Purposes   | 
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         To Be Well Capitalized Under  Prompt Corrective Action  Provisions   | 
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       |   | 
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         Amount   | 
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         Ratio   | 
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         Amount   | 
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         Ratio   | 
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         Amount   | 
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         Ratio   | 
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       |   As of December 31, 2019:   | 
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       |   CET I Capital to Risk Weighted Assets:   | 
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         | 
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       |   Consolidated   | 
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       $ | 
       822,396 | 
         | 
         | 
         | 
       10.50 | 
         %   | 
         | 
       $ | 
       342,283 | 
         | 
         | 
         | 
       4.50 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       885,172 | 
         | 
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         | 
       11.30 | 
         %   | 
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       342,269 | 
         | 
         | 
         | 
       4.50 | 
         %   | 
         | 
       $ | 
       494,389 | 
         | 
         | 
         | 
       6.50 | 
         %   | 
       
      
       |   Tier I Capital to Risk Weighted Assets:   | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
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         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
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       |   Consolidated   | 
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         | 
       822,896 | 
         | 
         | 
         | 
       10.50 | 
         %   | 
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         | 
       456,377 | 
         | 
         | 
         | 
       6.00 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       885,674 | 
         | 
         | 
         | 
       11.31 | 
         %   | 
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         | 
       456,359 | 
         | 
         | 
         | 
       6.00 | 
         %   | 
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         | 
       608,479 | 
         | 
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         | 
       8.00 | 
         %   | 
       
      
       |   Total Capital to Risk Weighted Assets:   | 
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         | 
         | 
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         | 
         | 
         | 
         | 
         | 
         | 
         | 
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         | 
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       |   Consolidated   | 
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         | 
       964,683 | 
         | 
         | 
         | 
       12.31 | 
         %   | 
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         | 
       608,502 | 
         | 
         | 
         | 
       8.00 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       962,758 | 
         | 
         | 
         | 
       12.29 | 
         %   | 
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       608,479 | 
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       8.00 | 
         %   | 
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       760,598 | 
         | 
         | 
         | 
       10.00 | 
         %   | 
       
      
       |   Tier I Capital to Average Assets:   | 
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         | 
         | 
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         | 
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         | 
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         | 
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       |   Consolidated   | 
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         | 
       822,896 | 
         | 
         | 
         | 
       9.13 | 
         %   | 
         | 
         | 
       356,012 | 
         | 
         | 
         | 
       4.00 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       885,674 | 
         | 
         | 
         | 
       9.83 | 
         %   | 
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       355,998 | 
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       4.00 | 
         %   | 
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       444,997 | 
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       5.00 | 
         %   | 
       
      
       |   | 
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         | 
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       |   As of December 31, 2018:   | 
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         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
       
      
       |   CET I Capital to Risk Weighted Assets:   | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
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         | 
         | 
         | 
         | 
         | 
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         | 
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       |   Consolidated   | 
         | 
       $ | 
       705,203 | 
         | 
         | 
         | 
       10.12 | 
         %   | 
         | 
       $ | 
       313,564 | 
         | 
         | 
         | 
       4.50 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       768,614 | 
         | 
         | 
         | 
       11.03 | 
         %   | 
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         | 
       313,554 | 
         | 
         | 
         | 
       4.50 | 
         %   | 
         | 
       $ | 
       452,911 | 
         | 
         | 
         | 
       6.50 | 
         %   | 
       
      
       |   Tier I Capital to Risk Weighted Assets:   | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
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       |   Consolidated   | 
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         | 
       705,705 | 
         | 
         | 
         | 
       10.13 | 
         %   | 
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         | 
       418,086 | 
         | 
         | 
         | 
       6.00 | 
         %   | 
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         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
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         | 
       769,116 | 
         | 
         | 
         | 
       11.04 | 
         %   | 
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         | 
       418,071 | 
         | 
         | 
         | 
       6.00 | 
         %   | 
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         | 
       557,428 | 
         | 
         | 
         | 
       8.00 | 
         %   | 
       
      
       |   Total Capital to Risk Weighted Assets:   | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
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       |   Consolidated   | 
         | 
         | 
       839,471 | 
         | 
         | 
         | 
       12.05 | 
         %   | 
         | 
         | 
       557,448 | 
         | 
         | 
         | 
       8.00 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       838,216 | 
         | 
         | 
         | 
       12.03 | 
         %   | 
         | 
         | 
       557,428 | 
         | 
         | 
         | 
       8.00 | 
         %   | 
         | 
         | 
       696,786 | 
         | 
         | 
         | 
       10.00 | 
         %   | 
       
      
       |   Tier I Capital to Average Assets:   | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
         | 
       
      
       |   Consolidated   | 
         | 
         | 
       705,705 | 
         | 
         | 
         | 
       9.07 | 
         %   | 
         | 
         | 
       311,214 | 
         | 
         | 
         | 
       4.00 | 
         %   | 
         | 
         | 
       N/A | 
         | 
         | 
         | 
       N/A | 
         | 
       
      
       |   ServisFirst Bank   | 
         | 
         | 
       769,116 | 
         | 
         | 
         | 
       9.89 | 
         %   | 
         | 
         | 
       311,206 | 
         | 
         | 
         | 
       4.00 | 
         %   | 
         | 
         | 
       389,007 | 
         | 
         | 
         | 
       5.00 | 
         %   | 
       
     
     
   
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