Capital of the Operating Partnership (Details Textual) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020		Sep. 30, 2019	Sep. 30, 2020	Mar. 31, 2020		Dec. 31, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018
Limited Partners' Capital Account [Line Items]
Partnership units (in shares)	127,051,238				127,051,238
Common stock, shares outstanding (in shares)	117,940,155				117,940,155			116,496,016
Minority interest increase (decrease) from redemptions number of units (in shares)					1,940,007
Equity redemption of OP Units, cash (in shares)					116,657
Equity redemption of OP Units cash dollars					$ 2.0
Equity Redemption of OP Units (in shares)					1,823,350
ROIC
Limited Partners' Capital Account [Line Items]
ROIC ownership percentage in ROIP LP					92.80%
Common Stock
Limited Partners' Capital Account [Line Items]
Common stock, shares outstanding (in shares)	117,940,155	117,640,038		115,324,655	117,940,155	116,120,704		116,496,016		114,307,789		114,311,788		113,992,837
Equity Redemption of OP Units (in shares)	301,517	1,521,833		80,000	1,823,350
OP Units
Limited Partners' Capital Account [Line Items]
Non-controlling interest redemption value	$ 95.2				$ 95.2
Redemption value (usd per share)	$ 10.45				$ 10.45
Retail Opportunity Investments Partnership L.P.
Limited Partners' Capital Account [Line Items]
Equity Redemption of OP Units (in shares)	301,517
Limited Partner’s Capital | Retail Opportunity Investments Partnership L.P.
Limited Partners' Capital Account [Line Items]
Partnership units (in shares)	9,111,083	9,412,600	[1]	11,227,041	9,111,083	10,934,433	[1]	11,051,090	[1]	11,407,041	[1]	11,407,041	[1]	11,477,041	[1]
Equity Redemption of OP Units (in shares)	301,517	1,521,833		80,000

[1] Consists of limited partnership interests held by third parties.