Quarterly Results of Operations (Unaudited) (Details) - Quarterly Results of Operations for the Operating Partnership - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Results of Operations (Unaudited) (Details) - Quarterly Results of Operations for the Operating Partnership [Line Items]
Total revenues	$ 75,158	$ 73,904	$ 72,341	$ 74,395	$ 72,754	$ 67,966	$ 66,640	$ 65,900	$ 295,798	$ 273,260	$ 237,189
Net income attributable to the Operating Partnership	$ 11,568	$ 15,647	$ 8,102	$ 11,824	$ 12,113	$ 10,127	$ 9,197	$ 11,251	$ 47,141	$ 42,688	$ 36,430
Earnings per unit - basic and diluted (in usd per share)	$ 0.09	$ 0.12	$ 0.06	$ 0.09	$ 0.10	$ 0.08	$ 0.08	$ 0.09	$ 0.38	$ 0.35	$ 0.31
Retail Opportunity Investments Partnership L.P.
Quarterly Results of Operations (Unaudited) (Details) - Quarterly Results of Operations for the Operating Partnership [Line Items]
Total revenues	$ 75,158	$ 73,904	$ 72,341	$ 74,395	$ 72,754	$ 67,966	$ 66,640	$ 65,900	$ 295,798	$ 273,260	$ 237,189
Net income attributable to the Operating Partnership	$ 11,568	$ 15,647	$ 8,102	$ 11,824	$ 12,113	$ 10,127	$ 9,197	$ 11,251	$ 47,141	$ 42,688	$ 36,430
Earnings per unit - basic and diluted (in usd per share)	$ 0.09	$ 0.12	$ 0.06	$ 0.09	$ 0.10	$ 0.08	$ 0.08	$ 0.09	$ 0.38	$ 0.35	$ 0.31