Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Officer	Common Stock	Additional paid-in capital	Accumulated dividends in excess of earnings	Accumulated dividends in excess of earnings Officer	Accumulated other comprehensive (loss) income	Non- controlling interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total (in shares)			99,531,034
Balance at Dec. 31, 2015	$ 1,131,342		$ 10	$ 1,166,395	$ (122,991)		$ (6,743)	$ 94,671
Balance (in shares) at Dec. 31, 2015			99,531,034
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the 2009 Equity Incentive 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
Issuance of OP Units to non-controlling interests	48,175							48,175
Redemption of OP Units (in shares)			755,762
Redemption of OP Units	15,990			15,990				(15,990)
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 (in shares)			8,757,254
Proceeds from the issuance of common stock	184,881		$ 1	184,880
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)			99,531,034
Total	1,308,855		$ 11	1,357,910	(165,951)		(3,729)	120,614
Proceeds from repayment of promissory note receivable secured by equity	6,710							6,710
Balance (in shares) at Dec. 31, 2016			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
Shares issued under the 2009 Equity Incentive Plan (in shares)			353,261
Shares issued under the 2009 Equity Incentive 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
Issuance of OP Units to non-controlling interests	49,599							49,599
Redemption of OP Units	50,155
Equity redemption and exchange of OP Units (in shares)			2,555,933
Equity redemption and exchange of OP Units				50,155				(50,155)
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 (in shares)			212,825
Proceeds from the issuance of common stock	4,481		$ 0	4,481
Registration expenditures	(1,045)			(1,045)
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)	112,347,451		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
Shares issued under the 2009 Equity Incentive Plan (in shares)			397,861
Shares issued under the 2009 Equity Incentive Plan	$ 269			269
Shares withheld for employee taxes (in shares)			(70,168)
Shares withheld for employee taxes	(1,400)			(1,400)
Cancellation of restricted stock (in shares)			(8,997)
Stock based compensation expense	7,392			7,392
Redemption of OP Units	0
Cash redemption for non-controlling interests	(3,713)							(3,713)
Adjustment to non-controlling interests ownership in Operating Partnership				(2,904)				2,904
Proceeds from the issuance of common stock (in shares)			1,326,690
Proceeds from the issuance of common stock	25,703			25,703
Registration expenditures	(570)			(570)
Cash dividends	(97,473)	$ (267)			(88,417)	$ (267)		(9,056)
Net income attributable to Retail Opportunity Investments Corp.	42,736				42,736
Net income attributable to non-controlling interests	4,405							4,405
Other comprehensive income	$ 1,705						1,705
Total (in shares)	112,347,451		112,347,451
Balance (in shares) at Dec. 31, 2018	113,992,837		113,992,837
Balance at Dec. 31, 2018	$ 1,308,428		$ 11	$ 1,441,080	$ (256,438)		$ 3,561	$ 120,214
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total (in shares)	113,992,837		113,992,837