Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2022	Mar. 11, 2023	Jun. 30, 2022
Document Information [Line Items]
Entity Central Index Key	0001035976
Entity Registrant Name	FNCB BANCORP, INC.
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2022
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity File Number	001-38408
Entity Incorporation, State or Country Code	PA
Entity Tax Identification Number	23-2900790
Entity Address, Address Line One	102 E. Drinker St.
Entity Address, City or Town	Dunmore
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	18512
City Area Code	570
Local Phone Number	346-7667
Title of 12(b) Security	Common Stock $1.25 Par Value
Trading Symbol	FNCB
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 129,632,432
Entity Common Stock, Shares Outstanding		19,682,689
Auditor Name	Baker Tilly US, LLP
Auditor Location	Iselin, New Jersey
Auditor Firm ID	23