Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 19, 2021	Jun. 30, 2020
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report.	false
Document Period End Date	Dec. 31, 2020
Entity File Number	001-38290
Entity Registrant Name	Sterling Bancorp, Inc.
Entity Incorporation, State or Country Code	MI
Entity Tax Identification Number	38-3163775
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 55.2
Entity Address, Address Line One	One Towne Square
Entity Address, Address Line Two	Suite 1900
Entity Address, City or Town	Southfield
Entity Address, State or Province	MI
Entity Address, Postal Zip Code	48076
City Area Code	248
Local Phone Number	355-2400
Title of 12(b) Security	Common Stock
Trading Symbol	SBT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		50,004,490
Entity Central Index Key	0001680379
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
ICFR Auditor Attestation Flag	false