Organization, Basis of Presentation and Summary of Significant Accounting Policies (Reconciliation Between Basic and Diluted EPS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 13,136	$ 14,583
Less income attributable to non-controlling interests	(1,134)	(1,333)
Less earnings allocated to unvested shares	(127)	(114)
Net income available for common stockholders, basic	11,875	13,136
Less earnings allocated to unvested shares	(127)	(114)
Net income available for common stockholders, diluted	$ 13,009	$ 14,469
Denominator:
Denominator for basic EPS – weighted average common equivalent shares (in shares)	115,970,461	113,680,670
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	127,181,333	125,440,770
Retail Opportunity Investments Partnership L.P.
Numerator:
Net income	$ 13,136	$ 14,583
Less earnings allocated to unvested shares	(127)	(114)
Net income available to unitholders, basic and diluted	$ 13,009	$ 14,469
Denominator:
Denominator for basic EPS – weighted average common equivalent shares (in shares)	126,947,461	125,126,600
Denominator for diluted EPS – weighted average common equivalent shares (in shares)	127,181,333	125,440,770
OP units
Denominator:
OP units (in shares)	10,977,000	11,445,930
Performance-based restricted stock awards and LTIP Units
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	218,881	219,762
Performance-based restricted stock awards and LTIP Units | Retail Opportunity Investments Partnership L.P.
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	218,881	219,762
Stock options
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	14,991	94,408
Stock options | Retail Opportunity Investments Partnership L.P.
Denominator:
Incremental common shares attributable to dilutive effect of share-based payment arrangements (in shares)	14,991	94,408