Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Feb. 11, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	RETAIL OPPORTUNITY INVESTMENTS CORP.
Entity File Number	001-33749
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	26-0500600
Entity Address, Address Line One	11250 El Camino Real
Entity Address, City or Town	San Diego,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92130
City Area Code	858
Local Phone Number	677-0900
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	ROIC
Security Exchange Name	NASDAQ
Entity Public Float			$ 2.1
Entity Common Stock, Shares Outstanding		122,802,342
Entity Central Index Key	0001407623
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Retail Opportunity Investments Partnership L.P.
Document Information [Line Items]
Current Fiscal Year End Date	--12-31
Entity Registrant Name	RETAIL OPPORTUNITY INVESTMENTS PARTNERSHIP, LP
Entity File Number	333-189057-01
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-2969738
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	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Central Index Key	0001577230
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false