Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 03, 2020	Jun. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Entity Registrant Name	SB ONE BANCORP
Entity Central Index Key	0001028954
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 210,391,032
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		9,415,505