Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2016
Mar. 10, 2017
Jun. 30, 2016
Document Information [Line Items]      
Entity Registrant Name FNCB BANCORP, INC.    
Entity Central Index Key 0001035976    
Trading Symbol fncb    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Common Stock, Shares Outstanding (in shares)   16,661,978  
Entity Public Float     $ 80,096,019
Document Type 10-K    
Document Period End Date Dec. 31, 2016    
Document Fiscal Year Focus 2016    
Document Fiscal Period Focus FY    
Amendment Flag false