Organization, Basis of Presentation and Summary of Significant Accounting Policies (Reconciliation Between Basic and Diluted EPS) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income	$ 9,197	$ 8,638	$ 20,448	$ 17,563
Less income attributable to non-controlling interests	888	934	1,969	1,832
Less earnings allocated to unvested shares	(80)	(68)	(160)	(136)
Net income available for common stockholders, basic	8,229	7,636	18,319	15,595
Less earnings allocated to unvested shares	(80)	(68)	(160)	(136)
Net income available for common stockholders, diluted	$ 9,117	$ 8,570	$ 20,288	$ 17,427
Denominator:
Denominator for basic EPS – weighted average common equivalent shares (in shares)	109,267,356	100,166,136	109,247,194	99,788,706
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	121,237,934	112,642,901	121,156,169	111,688,972
Retail Opportunity Investments Partnership L.P.
Numerator:
Net income	$ 9,197	$ 8,638	$ 20,448	$ 17,563
Less earnings allocated to unvested shares	(80)	(68)	(160)	(136)
Net income available to unitholders, basic and diluted	$ 9,117	$ 8,570	$ 20,288	$ 17,427
Denominator:
Denominator for basic EPS – weighted average common equivalent shares (in shares)	120,947,667	112,358,245	120,872,242	111,431,696
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	121,237,934	112,642,901	121,156,169	111,688,972
OP units
Denominator:
OP units (in shares)	11,680,311	12,192,109	11,625,048	11,642,990
Restricted stock awards – performance-based
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	159,526	152,675	150,613	131,783
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)	159,526	152,675	150,613	131,783
Stock options
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	130,741	131,981	133,314	125,493
Stock options | Retail Opportunity Investments Partnership L.P.
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	130,741	131,981	133,314	125,493