Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Officer	Common Stock	Additional paid-in capital	Retained earnings (Accumulated deficit)	Retained earnings (Accumulated deficit) Officer	Accumulated other comprehensive loss	Non- controlling interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total (in shares)			92,991,333
Balance at Dec. 31, 2014	$ 962,782		$ 9	$ 1,013,561	$ (80,976)		$ (8,882)	$ 39,070
Balance (in shares) at Dec. 31, 2014			92,991,333
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the 2009 Plan (in shares)			381,577
Shares withheld for employee taxes (in shares)			(78,570)
Shares withheld for employee taxes	(1,317)			(1,317)
Cancellation of restricted stock (in shares)			(2,832)
Stock based compensation expense	4,684			4,684
Redemption of OP Units (in shares)			174,959
Redemption of OP Units	3,184			3,184				(3,184)
Issuance of OP Units to non-controlling interests	116,640							116,640
Adjustment to non-controlling interests ownership in Operating Partnership				49,609				(49,609)
Proceeds from the issuance of common stock	101,293		$ 1	101,292
Proceeds from the issuance of common stock (in shares)			6,064,567
Registration expenditures	(4,618)			(4,618)
Cash dividends	(68,482)	$ (161)			(65,718)	$ (161)		(2,764)
Net income attributable to Retail Opportunity Investments Corp.	23,864				23,864
Net income attributable to non-controlling interests	1,228							1,228
Other comprehensive income	2,139						2,139
Total (in shares)			92,991,333
Total	1,138,052		$ 10	1,166,395	(122,991)		(6,743)	101,381
Less: Promissory note secured by equity	(6,710)
Balance (in shares) at Dec. 31, 2015			99,531,034
Balance at Dec. 31, 2015	1,131,342		$ 10	1,166,395	(122,991)		(6,743)	94,671
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total (in shares)			99,531,034
Shares issued under the 2009 Plan (in shares)			341,306
Shares withheld for employee taxes (in shares)			(76,262)
Shares withheld for employee taxes	(1,368)			(1,368)
Cancellation of restricted stock (in shares)			(7,332)
Stock based compensation expense	4,916			4,916
Redemption of OP Units (in shares)			755,762
Redemption of OP Units	15,990			15,990				(15,990)
Issuance of OP Units to non-controlling interests	48,175							48,175
Cash redemption for non-controlling interests	(7,182)							(7,182)
Adjustment to non-controlling interests ownership in Operating Partnership				(5,627)				5,627
Proceeds from the issuance of common stock	184,881		$ 1	184,880
Proceeds from the issuance of common stock (in shares)			8,757,254
Registration expenditures	(7,276)			(7,276)
Cash dividends	(83,900)	(177)			(75,537)	(177)		(8,363)
Net income attributable to Retail Opportunity Investments Corp.	32,754				32,754
Net income attributable to non-controlling interests	3,676							3,676
Other comprehensive income	$ 3,014						3,014
Total (in shares)	109,301,762		99,531,034
Total	$ 1,308,855		$ 11	1,357,910	(165,951)		(3,729)	120,614
Less: Promissory note secured by equity	$ 6,710							6,710
Balance (in shares) at Dec. 31, 2016	109,301,762		109,301,762
Balance at Dec. 31, 2016	$ 1,315,565		$ 11	1,357,910	(165,951)		(3,729)	127,324
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total (in shares)	109,301,762		109,301,762
Shares issued under the 2009 Plan (in shares)			353,261
Shares issued under the 2009 Plan	$ 44			44
Shares withheld for employee taxes (in shares)			(74,331)
Shares withheld for employee taxes	(1,571)			(1,571)
Cancellation of restricted stock (in shares)			(1,999)
Stock based compensation expense	$ 6,190			6,190
Redemption of OP Units (in shares)	150,503		150,503
Redemption of OP Units	$ 50,155
Equity redemption and exchange of OP Units				50,155				(50,155)
Issuance of OP Units to non-controlling interests	49,599							49,599
Equity redemption and exchange of OP Units (in shares)			2,555,933
Cash redemption for non-controlling interests	(150)							(150)
Adjustment to non-controlling interests ownership in Operating Partnership				(3,574)				3,574
Proceeds from the issuance of common stock	4,481		$ 0	4,481
Proceeds from the issuance of common stock (in shares)			212,825
Registration expenditures	(1,045)			(1,045)				0
Cash dividends	(91,510)	$ (235)			(82,781)	$ (235)		(8,729)
Net income attributable to Retail Opportunity Investments Corp.	38,477				38,477
Net income attributable to non-controlling interests	4,211							4,211
Other comprehensive income	$ 5,585						5,585
Total (in shares)	109,301,762		109,301,762
Balance (in shares) at Dec. 31, 2017	112,347,451		112,347,451
Balance at Dec. 31, 2017	$ 1,329,641		$ 11	$ 1,412,590	$ (210,490)		$ 1,856	$ 125,674
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total (in shares)	112,347,451		112,347,451