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Note 2 - Real Estate Investments (Details) - Operating Results Included in the Company's Historical Consolidated Statement of Operations for Properties Acquired During the Reported Periods (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Income Statements, Captions [Line Items]
Revenues	$ 41,742,670us-gaap_Revenues	$ 40,855,871us-gaap_Revenues	$ 36,914,834us-gaap_Revenues	$ 36,350,136us-gaap_Revenues	$ 33,636,485us-gaap_Revenues	$ 27,147,631us-gaap_Revenues	$ 26,063,466us-gaap_Revenues	$ 24,384,449us-gaap_Revenues	$ 155,863,511us-gaap_Revenues	$ 111,232,031us-gaap_Revenues	$ 75,095,687us-gaap_Revenues
Property operating and other expenses									25,035,765	19,749,972	12,779,758
Depreciation and amortization									58,434,981	40,397,895	29,074,709
Net income attributable to Retail Opportunity Investments Corp.	4,586,763us-gaap_NetIncomeLoss	6,748,847us-gaap_NetIncomeLoss	5,833,750us-gaap_NetIncomeLoss	3,131,685us-gaap_NetIncomeLoss	3,790,372us-gaap_NetIncomeLoss	25,262,291us-gaap_NetIncomeLoss	2,471,012us-gaap_NetIncomeLoss	2,289,886us-gaap_NetIncomeLoss	20,301,045us-gaap_NetIncomeLoss	33,813,561us-gaap_NetIncomeLoss	7,892,613us-gaap_NetIncomeLoss
Attributable to Acquired Properties During the Reporting Periods [Member]
Condensed Income Statements, Captions [Line Items]
Revenues									16,234,264	15,813,152
Property operating and other expenses									4,643,335	6,010,175
Depreciation and amortization									7,673,714	7,655,138
Net income attributable to Retail Opportunity Investments Corp.									$ 3,917,215	$ 2,147,839