Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 53,683,000	$ 47,141,000	$ 42,688,000
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	97,559,000	100,838,000	96,256,000
Amortization of deferred financing costs and mortgage premiums, net	2,076,000	1,899,000	2,026,000
Straight-line rent adjustment	(3,083,000)	(5,380,000)	(6,176,000)
Amortization of above and below market rent	(15,618,000)	(13,965,000)	(17,078,000)
Amortization relating to stock based compensation	8,567,000	7,392,000	6,190,000
Provisions for tenant credit losses	1,969,000	1,729,000	1,191,000
Other noncash interest expense	524,000	1,674,000	2,139,000
Gain on sale of real estate	(13,175,000)	(5,890,000)	0
Change in operating assets and liabilities:
Tenant and other receivables	543,000	(57,000)	(2,452,000)
Prepaid expenses	962,000	(1,344,000)	464,000
Accounts payable and accrued expenses	303,000	(1,622,000)	456,000
Other assets and liabilities, net	(2,271,000)	(1,497,000)	3,234,000
Net cash provided by operating activities	132,039,000	130,918,000	128,938,000
CASH FLOWS FROM INVESTING ACTIVITIES
Investments in real estate	(11,601,000)	(44,195,000)	(263,366,000)
Proceeds from sale of real estate	58,930,000	26,880,000	0
Improvements to properties	(35,177,000)	(39,240,000)	(54,097,000)
Deposits on real estate acquisitions, net	0	500,000	(500,000)
Proceeds on repayment of mortgage note receivable	250,000	0	0
Net cash provided by (used in) investing activities	12,402,000	(56,055,000)	(317,963,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal repayments on mortgages	(551,000)	(19,612,000)	(8,848,000)
Proceeds from draws on credit facility	101,000,000	177,000,000	327,500,000
Payments on credit facility	(173,000,000)	(164,500,000)	(282,000,000)
Proceeds from issuance of Senior Notes	0	0	250,000,000
Redemption of OP Units	(5,043,000)	(3,713,000)	(150,000)
Distributions to OP Unitholders	(8,921,000)	(9,056,000)	(8,729,000)
Deferred financing and other costs	(2,804,000)	0	(3,845,000)
Proceeds from the issuance of common stock	34,162,000	25,703,000	4,481,000
Registration expenditures	(478,000)	(570,000)	(1,225,000)
Dividends paid to common shareholders	(90,753,000)	(88,500,000)	(82,917,000)
Common shares issued under the Equity Incentive Plan	1,942,000	269,000	44,000
Shares withheld for employee taxes	(1,986,000)	(1,400,000)	(1,571,000)
Net cash (used in) provided by financing activities	(146,432,000)	(84,379,000)	192,740,000
Net (decrease) increase in cash, cash equivalents and restricted cash	(1,991,000)	(9,516,000)	3,715,000
Cash, cash equivalents and restricted cash at beginning of period	7,449,000	16,965,000	13,250,000
Cash, cash equivalents and restricted cash at end of period	5,458,000	7,449,000	16,965,000
Reconciliation of Cash and Cash Equivalents [Abstract]
Total cash, cash equivalents and restricted cash shown in Statements of Cash Flows	7,449,000	7,449,000	16,965,000
Retail Opportunity Investments Partnership L.P.
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	53,683,000	47,141,000	42,688,000
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	97,559,000	100,838,000	96,256,000
Amortization of deferred financing costs and mortgage premiums, net	2,076,000	1,899,000	2,026,000
Straight-line rent adjustment	(3,083,000)	(5,380,000)	(6,176,000)
Amortization of above and below market rent	(15,618,000)	(13,965,000)	(17,078,000)
Amortization relating to stock based compensation	8,567,000	7,392,000	6,190,000
Provisions for tenant credit losses	1,969,000	1,729,000	1,191,000
Other noncash interest expense	524,000	1,674,000	2,139,000
Gain on sale of real estate	(13,175,000)	(5,890,000)	0
Change in operating assets and liabilities:
Tenant and other receivables	543,000	(57,000)	(2,452,000)
Prepaid expenses	962,000	(1,344,000)	464,000
Accounts payable and accrued expenses	303,000	(1,622,000)	456,000
Other assets and liabilities, net	(2,271,000)	(1,497,000)	3,234,000
Net cash provided by operating activities	132,039,000	130,918,000	128,938,000
CASH FLOWS FROM INVESTING ACTIVITIES
Investments in real estate	(11,601,000)	(44,195,000)	(263,366,000)
Proceeds from sale of real estate	58,930,000	26,880,000	0
Improvements to properties	(35,177,000)	(39,240,000)	(54,097,000)
Deposits on real estate acquisitions, net	0	500,000	(500,000)
Proceeds on repayment of mortgage note receivable	250,000	0	0
Net cash provided by (used in) investing activities	12,402,000	(56,055,000)	(317,963,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal repayments on mortgages	(551,000)	(19,612,000)	(8,848,000)
Proceeds from draws on credit facility	101,000,000	177,000,000	327,500,000
Payments on credit facility	(173,000,000)	(164,500,000)	(282,000,000)
Proceeds from issuance of Senior Notes	0	0	250,000,000
Redemption of OP Units	(5,043,000)	(3,713,000)	(150,000)
Distributions to OP Unitholders	(99,674,000)	(97,556,000)	(91,646,000)
Deferred financing and other costs	(2,804,000)	0	(3,845,000)
Proceeds from the issuance of common stock	34,162,000	25,703,000	4,481,000
Registration expenditures	(478,000)	(570,000)	(1,225,000)
Common shares issued under the Equity Incentive Plan	1,942,000	269,000	44,000
Shares withheld for employee taxes	(1,986,000)	(1,400,000)	(1,571,000)
Net cash (used in) provided by financing activities	(146,432,000)	(84,379,000)	192,740,000
Net (decrease) increase in cash, cash equivalents and restricted cash	(1,991,000)	(9,516,000)	3,715,000
Cash, cash equivalents and restricted cash at beginning of period	7,449,000	16,965,000	13,250,000
Cash, cash equivalents and restricted cash at end of period	5,458,000	7,449,000	16,965,000
Reconciliation of Cash and Cash Equivalents [Abstract]
Total cash, cash equivalents and restricted cash shown in Statements of Cash Flows	$ 7,449,000	$ 7,449,000	$ 13,250,000