Consolidated Statements of Operations and Comprehensive Income - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Rental revenue	$ 291,263,000	$ 289,601,000	$ 269,382,000
Other income	3,777,000	6,197,000	3,878,000
Total revenues	295,040,000	295,798,000	273,260,000
Operating expenses
Property operating	43,662,000	43,851,000	39,151,000
Property taxes	32,388,000	32,349,000	29,663,000
Depreciation and amortization	97,559,000	100,838,000	96,256,000
General and administrative expenses	17,831,000	14,918,000	14,103,000
Acquisition transaction costs	0	0	4,000
Other expense	1,405,000	478,000	418,000
Total operating expenses	192,845,000	192,434,000	179,595,000
Gain on sale of real estate	13,175,000	5,890,000	0
Operating income	115,370,000	109,254,000	93,665,000
Non-operating expenses
Interest expense and other finance expenses	(61,687,000)	(62,113,000)	(50,977,000)
Net income	53,683,000	47,141,000	42,688,000
Net income attributable to non-controlling interests	(4,839,000)	(4,405,000)	(4,211,000)
Net Income Attributable to Retail Opportunity Investments Corp.	$ 48,844,000	$ 42,736,000	$ 38,477,000
Earnings per share/unit - basic and diluted (in usd per share)	$ 0.42	$ 0.38	$ 0.35
Dividends per share (in dollars per share)	$ 0.7880	$ 0.7800	$ 0.7500
Comprehensive income:
Net income	$ 53,683,000	$ 47,141,000	$ 42,688,000
Unrealized swap derivative (loss) gain arising during the period	(7,348,000)	1,648,000	3,665,000
Reclassification adjustment for amortization of interest expense included in net income	(345,000)	57,000	1,920,000
Other comprehensive (loss) income	(7,693,000)	1,705,000	5,585,000
Comprehensive income	45,990,000	48,846,000	48,273,000
Comprehensive income attributable to non-controlling interests	(4,839,000)	(4,405,000)	(4,211,000)
Comprehensive income attributable to Retail Opportunity Investments Corp.	41,151,000	44,441,000	44,062,000
Retail Opportunity Investments Partnership L.P.
Revenues
Rental revenue	291,263,000	289,601,000	269,382,000
Other income	3,777,000	6,197,000	3,878,000
Total revenues	295,040,000	295,798,000	273,260,000
Operating expenses
Property operating	43,662,000	43,851,000	39,151,000
Property taxes	32,388,000	32,349,000	29,663,000
Depreciation and amortization	97,559,000	100,838,000	96,256,000
General and administrative expenses	17,831,000	14,918,000	14,103,000
Acquisition transaction costs	0	0	4,000
Other expense	1,405,000	478,000	418,000
Total operating expenses	192,845,000	192,434,000	179,595,000
Gain on sale of real estate	13,175,000	5,890,000	0
Operating income	115,370,000	109,254,000	93,665,000
Non-operating expenses
Interest expense and other finance expenses	(61,687,000)	(62,113,000)	(50,977,000)
Net income	$ 53,683,000	$ 47,141,000	$ 42,688,000
Earnings per share/unit - basic and diluted (in usd per share)	$ 0.42	$ 0.38	$ 0.35
Dividends per share (in dollars per share)	$ 0.7880	$ 0.7800	$ 0.7500
Comprehensive income:
Net income	$ 53,683,000	$ 47,141,000	$ 42,688,000
Unrealized swap derivative (loss) gain arising during the period	(7,348,000)	1,648,000	3,665,000
Reclassification adjustment for amortization of interest expense included in net income	(345,000)	57,000	1,920,000
Other comprehensive (loss) income	(7,693,000)	1,705,000	5,585,000
Comprehensive income	$ 45,990,000	$ 48,846,000	$ 48,273,000