XML 11 R1.htm IDEA: XBRL DOCUMENT v3.5.0.2
Document and Entity Information - shares
 6 Months Ended
Jun. 30, 2016
Jul. 28, 2016
Document and Entity Information [Abstract]    
Entity Registrant Name First Business Financial Services, Inc.  
Entity Central Index Key 0001521951  
Current Fiscal Year End Date --12-31  
Document Type 10-Q  
Document Period End Date Jun. 30, 2016  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   8,703,942