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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 8,215	$ 7,837	$ 25,778	$ 17,624
Net income attributable to non-controlling interests	813	295	2,645	681
Less earnings allocated to unvested shares	(67)	(58)	(204)	(173)
Net income available for common stockholders, basic	7,335	7,484	22,929	16,770
Less earnings allocated to unvested shares	(67)	(58)	(204)	(173)
Net income available for common stockholders, diluted	$ 8,148	$ 7,779	$ 25,574	$ 17,451
Denominator for basic EPS – weighted average common equivalent shares (in shares)	107,745,991	96,722,628	102,460,495	94,479,375
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	120,073,749	100,755,463	114,509,147	98,560,981
Retail Opportunity Investments Partnership L.P.
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 8,215	$ 7,837	$ 25,778	$ 17,624
Less earnings allocated to unvested shares	(67)	(58)	(204)	(173)
Net income available to unitholders, basic and diluted	$ 8,148	$ 7,779	$ 25,574	$ 17,451
Denominator for basic EPS – weighted average common equivalent shares (in shares)	119,761,191	100,493,942	114,228,460	98,305,085
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	120,073,749	100,755,463	114,509,147	98,560,981
OP units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
OP units (in shares)	12,015,200	3,771,314	11,767,965	3,825,710
Restricted stock awards – performance-based
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	166,949	163,167	147,751	153,191
Restricted stock awards – performance-based | Retail Opportunity Investments Partnership L.P.
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	166,949	163,167	147,751	153,191
Stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	145,609	98,354	132,936	102,705
Stock options | Retail Opportunity Investments Partnership L.P.
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	145,609	98,354	132,936	102,705