Real Estate Investments (Operating Results Included in the Company's Historical Consolidated Statement of Operations for Properties Acquired During the Reported Periods) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Business Acquisition [Line Items]
Revenues	$ 3,491
Net income attributable to Retail Opportunity Investments Corp.	$ 668
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Revenues		$ 6,887
Net income attributable to Retail Opportunity Investments Corp.		$ 1,561