Capital of the Operating Partnership	12 Months Ended
Dec. 31, 2017
Partners' Capital Notes [Abstract]
Capital of the Operating Partnership	Capital of the Operating Partnership As of December 31, 2017, the Operating Partnership had 124,026,442 OP Units outstanding. ROIC owned an approximate 90.5% interest in the Operating Partnership at December 31, 2017, or 112,347,451 OP Units. The remaining 11,678,991 OP Units are owned by other limited partners. A share of ROIC’s common stock and the OP Units have essentially the same economic characteristics as they share equally in the total net income or loss and distributions of the Operating Partnership. As of December 31, 2017, subject to certain exceptions, holders are able to redeem their OP Units, at the option of ROIC, for cash or for unregistered shares of ROIC common stock on a one-for-one basis. If cash is paid in the redemption, the redemption price is equal to the average closing price on the NASDAQ Stock Market for shares of ROIC’s common stock over the ten consecutive trading days immediately preceding the date a redemption notice is received by ROIC. In connection with the acquisitions of Fullerton Crossroads and Riverstone Marketplace, a portion of the consideration for the properties was funded through the issuance of 2,405,430 OP Units. On December 12, 2017, the Company issued 2,584,254 shares of common stock in exchange for the 2,405,430 OP Units previously issued and the rights to approximately $3.8 million of cash to be used to acquire a third property to be identified by the Company. During the year ended December 31, 2017, ROIC received notices of redemption for a total of 157,567 OP Units (excluding the OP Units exchanged, as described above). ROIC elected to redeem 150,503 OP Units for shares of ROIC common stock on a one-for-one basis, and accordingly, 150,503 shares of ROIC common stock were issued. ROIC elected to redeem the remaining 7,064 OP Units in cash. The redemption value of the OP Units owned by the limited partners as of December 31, 2017, not including ROIC, had such units been redeemed at December 31, 2017, was approximately $229.5 million, calculated based on the average closing price on the NASDAQ Stock Market of ROIC common stock for the ten consecutive trading days immediately preceding December 31, 2017, which amounted to $19.65 per share. Retail Opportunity Investments GP, LLC, ROIC’s wholly-owned subsidiary, is the sole general partner of the Operating Partnership, and as the parent company, ROIC has the full and complete authority over the Operating Partnership’s day-to-day management and control. As the sole general partner of the Operating Partnership, ROIC effectively controls the ability to issue common stock of ROIC upon redemption of any OP Units. The redemption provisions that permit ROIC to settle the redemption of OP Units in either cash or common stock, in the sole discretion of ROIC, are further evaluated in accordance with applicable accounting guidance to determine whether temporary or permanent equity classification on the balance sheet is appropriate. The Company evaluated this guidance, including the ability, in its sole discretion, to settle in unregistered shares of common stock, and determined that the OP Units meet the requirements to qualify for presentation as permanent equity.

Capital of the Operating Partnership

As of December 31, 2017, the Operating Partnership had 124,026,442 OP Units outstanding. ROIC owned an approximate 90.5% interest in the Operating Partnership at December 31, 2017, or 112,347,451 OP Units. The remaining 11,678,991 OP Units are owned by other limited partners. A share of ROIC’s common stock and the OP Units have essentially the same economic characteristics as they share equally in the total net income or loss and distributions of the Operating Partnership.

As of December 31, 2017, subject to certain exceptions, holders are able to redeem their OP Units, at the option of ROIC, for cash or for unregistered shares of ROIC common stock on a one-for-one basis. If cash is paid in the redemption, the redemption price is equal to the average closing price on the NASDAQ Stock Market for shares of ROIC’s common stock over the ten consecutive trading days immediately preceding the date a redemption notice is received by ROIC.

In connection with the acquisitions of Fullerton Crossroads and Riverstone Marketplace, a portion of the consideration for the properties was funded through the issuance of 2,405,430 OP Units. On December 12, 2017, the Company issued 2,584,254 shares of common stock in exchange for the 2,405,430 OP Units previously issued and the rights to approximately $3.8 million of cash to be used to acquire a third property to be identified by the Company.

During the year ended December 31, 2017, ROIC received notices of redemption for a total of 157,567 OP Units (excluding the OP Units exchanged, as described above). ROIC elected to redeem 150,503 OP Units for shares of ROIC common stock on a one-for-one basis, and accordingly, 150,503 shares of ROIC common stock were issued. ROIC elected to redeem the remaining 7,064 OP Units in cash.

The redemption value of the OP Units owned by the limited partners as of December 31, 2017, not including ROIC, had such units been redeemed at December 31, 2017, was approximately $229.5 million, calculated based on the average closing price on the NASDAQ Stock Market of ROIC common stock for the ten consecutive trading days immediately preceding December 31, 2017, which amounted to $19.65 per share.

Retail Opportunity Investments GP, LLC, ROIC’s wholly-owned subsidiary, is the sole general partner of the Operating Partnership, and as the parent company, ROIC has the full and complete authority over the Operating Partnership’s day-to-day management and control. As the sole general partner of the Operating Partnership, ROIC effectively controls the ability to issue common stock of ROIC upon redemption of any OP Units. The redemption provisions that permit ROIC to settle the redemption of OP Units in either cash or common stock, in the sole discretion of ROIC, are further evaluated in accordance with applicable accounting guidance to determine whether temporary or permanent equity classification on the balance sheet is appropriate. The Company evaluated this guidance, including the ability, in its sole discretion, to settle in unregistered shares of common stock, and determined that the OP Units meet the requirements to qualify for presentation as permanent equity.