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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Business Acquisition [Line Items]
Revenues	$ 59,354	$ 50,077	$ 174,119	$ 141,414
Net Income Attributable to Retail Opportunity Investments Corp.	7,402	$ 7,542	23,133	$ 16,943
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Revenues	4,923		8,180
Net Income Attributable to Retail Opportunity Investments Corp.	$ 626		$ 948