Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 30, 2018
Document Information [Line Items]
Entity Registrant Name	RETAIL OPPORTUNITY INVESTMENTS CORP
Trading Symbol	roic
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		113,996,474
Entity Public Float			$ 2.1
Amendment Flag	false
Entity Central Index Key	0001407623
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Retail Opportunity Investments Partnership L.P.
Document Information [Line Items]
Entity Registrant Name	Retail Opportunity Investments Partnerships L.P.
Document Type	10-K
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Entity Central Index Key	0001577230
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY