Document and Entity Information - shares
 3 Months Ended
Mar. 31, 2016
Apr. 15, 2016
Document and Entity Information    
Entity Registrant Name 1ST SOURCE CORP  
Entity Central Index Key 0000034782  
Document Type 10-Q  
Document Period End Date Mar. 31, 2016  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   25,849,257
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q1