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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Business Acquisition [Line Items]
Revenues	$ 58,671	$ 46,215	$ 114,765	$ 91,337
Net Income Attributable to Retail Opportunity Investments Corp.	7,704	$ 5,201	15,731	$ 9,401
Attributable to Acquired Properties During the Reporting Periods
Business Acquisition [Line Items]
Revenues	2,961		3,257
Net Income Attributable to Retail Opportunity Investments Corp.	$ 415		$ 327