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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Results of Operations (Unaudited) (Details) - Quarterly Results of Operations for the Operating Partnership [Line Items]
Total revenues	$ 73,619	$ 72,438	$ 72,930	$ 76,053	$ 75,158	$ 73,904	$ 72,341	$ 74,395	$ 295,040	$ 295,798	$ 273,260
Net income attributable to the Operating Partnership	$ 11,126	$ 19,628	$ 8,346	$ 14,583	$ 11,568	$ 15,647	$ 8,102	$ 11,824	$ 53,683	$ 47,141	$ 42,688
Earnings per unit - basic and diluted (in usd per share)	$ 0.09	$ 0.16	$ 0.07	$ 0.12	$ 0.09	$ 0.12	$ 0.06	$ 0.09	$ 0.42	$ 0.38	$ 0.35
Retail Opportunity Investments Partnership L.P.
Quarterly Results of Operations (Unaudited) (Details) - Quarterly Results of Operations for the Operating Partnership [Line Items]
Total revenues	$ 73,619	$ 72,438	$ 72,930	$ 76,053	$ 75,158	$ 73,904	$ 72,341	$ 74,395	$ 295,040	$ 295,798	$ 273,260
Net income attributable to the Operating Partnership	$ 11,126	$ 19,628	$ 8,346	$ 14,583	$ 11,568	$ 15,647	$ 8,102	$ 11,824	$ 53,683	$ 47,141	$ 42,688
Earnings per unit - basic and diluted (in usd per share)	$ 0.09	$ 0.16	$ 0.07	$ 0.12	$ 0.09	$ 0.12	$ 0.06	$ 0.09	$ 0.42	$ 0.38	$ 0.35