Capital of the Operating Partnership (Details Textual) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Limited Partners' Capital Account [Line Items]
Partnership units (in shares)		125,718,829
ROIC ownership percentage in ROIP LP		90.90%
Common stock, shares outstanding (in shares)		114,311,788	113,992,837
Equity redemption of OP Units, cash (in shares)		70,000
Equity redemption of OP Units cash dollars		$ 1.2
Common Stock
Limited Partners' Capital Account [Line Items]
Common stock, shares outstanding (in shares)		114,311,788	113,992,837	112,721,459	112,347,451
OP Units
Limited Partners' Capital Account [Line Items]
Non-controlling interest redemption value		$ 194.0
Redemption value (usd per share)		$ 17.01
Limited Partner’s Capital | Retail Opportunity Investments Partnership L.P.
Limited Partners' Capital Account [Line Items]
Partnership units (in shares)	[1]	11,407,041	11,477,041	11,678,991	11,678,991

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