Organization, Basis of Presentation and Summary of Significant Accounting Policies (Reconciliation Between Basic and Diluted EPS) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income	$ 10,127	$ 8,215	$ 30,575	$ 25,778
Less income attributable to non-controlling interests	978	813	2,947	2,645
Less earnings allocated to unvested shares	(80)	(67)	(239)	(204)
Net income available for common stockholders, basic	9,069	7,335	27,389	22,929
Less earnings allocated to unvested shares	(80)	(67)	(239)	(204)
Net income available for common stockholders, diluted	$ 10,047	$ 8,148	$ 30,336	$ 25,574
Denominator:
Denominator for basic EPS – weighted average common equivalent shares (in shares)	109,267,444	107,745,991	109,254,018	102,460,495
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	121,251,183	120,073,749	121,200,615	114,509,147
Retail Opportunity Investments Partnership L.P.
Numerator:
Net income	$ 10,127	$ 8,215	$ 30,575	$ 25,778
Less earnings allocated to unvested shares	(80)	(67)	(239)	(204)
Net income available to unitholders, basic and diluted	$ 10,047	$ 8,148	$ 30,336	$ 25,574
Denominator:
Denominator for basic EPS – weighted average common equivalent shares (in shares)	120,946,435	119,761,191	120,897,244	114,228,460
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	121,251,183	120,073,749	121,200,615	114,509,147
OP units
Denominator:
OP units (in shares)	11,678,991	12,015,200	11,643,226	11,767,965
Restricted stock awards – performance-based
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	177,670	166,949	172,089	147,751
Restricted stock awards – performance-based | Retail Opportunity Investments Partnership L.P.
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	177,670	166,949	172,089	147,751
Stock options
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	127,078	145,609	131,282	132,936
Stock options | Retail Opportunity Investments Partnership L.P.
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	127,078	145,609	131,282	132,936