Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Restricted Cash and Investments	$ 3,800	$ 0	$ 0
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	42,688	36,430	25,092
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	96,256	88,359	70,957
Amortization of deferred financing costs and mortgage premiums, net	2,026	2,088	662
Straight-line rent adjustment	(6,176)	(4,560)	(5,013)
Amortization of above and below market rent	(17,078)	(13,847)	(9,890)
Amortization relating to stock based compensation	6,190	4,916	4,684
Provisions for tenant credit losses	1,191	1,805	1,984
Other noncash interest expense	2,139	2,139	2,139
Change in operating assets and liabilities:
Restricted cash	(643)	66	264
Tenant and other receivables	(2,452)	(4,412)	(2,599)
Prepaid expenses	464	(1,363)	501
Accounts payable and accrued expenses	456	4,417	512
Other assets and liabilities, net	3,234	(1,356)	(2,376)
Net cash provided by operating activities	128,295	114,682	86,917
CASH FLOWS FROM INVESTING ACTIVITIES
Investments in real estate	(263,366)	(284,867)	(313,623)
Increase in restricted cash	(844)	35	23
Improvements to properties	(54,097)	(40,758)	(27,515)
Deposits on real estate acquisitions, net	(500)	500	4,000
Net cash used in investing activities	(322,607)	(325,090)	(337,115)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal repayments on mortgages	(8,848)	(7,816)	(84,308)
Proceeds from new mortgage loan	0	0	35,500
Proceeds from term loan	0	0	300,000
Proceeds from draws on credit facility	327,500	332,500	430,000
Payments on credit facility	(282,000)	(370,000)	(451,000)
Issuance of promissory note receivable	0	0	(6,710)
Proceeds on repayment of promissory note receivable	0	6,710	0
Redemption of OP Units	(150)	(38,820)	0
Distributions to OP Unitholders	(8,729)	(8,363)	(2,764)
Deferred financing and other costs	(3,845)	(266)	(1,849)
Proceeds from the issuance of OP Units in connection with issuance of common stock	4,481	184,881	101,293
Registration expenditures	(1,225)	(7,097)	(4,739)
Dividends paid to common shareholders	(82,917)	(75,672)	(65,837)
Shares withheld for employee taxes	(1,571)	(1,368)	(1,317)
Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options	44	0	0
Net cash provided by financing activities	192,740	214,689	248,269
Net (decrease) increase in cash and cash equivalents	(1,572)	4,281	(1,929)
Cash and cash equivalents at beginning of period	13,125	8,844	10,773
Cash and cash equivalents at end of period	11,553	13,125	8,844
Supplemental disclosure of cash activities:
Cash paid on gross receipts and income for federal and state purposes	253	206	241
Interest paid	46,271	34,275	31,996
Other non-cash investing and financing activities:
Issuance of OP Units in connection with acquisitions	49,599	46,140	150,315
Fair value of assumed mortgages upon acquisition	46,034	17,618	19,024
Intangible lease liabilities	45,456	32,615	37,480
Interest rate swap asset	3,446	875	0
Accrued real estate improvement costs	383	601	590
Equity redemption of OP Units	50,155	15,990	3,184
Retail Opportunity Investments Partnership L.P.
Increase (Decrease) in Restricted Cash and Investments	3,800	0	0
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	42,688	36,430	25,092
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	96,256	88,359	70,957
Amortization of deferred financing costs and mortgage premiums, net	2,026	2,088	662
Straight-line rent adjustment	(6,176)	(4,560)	(5,013)
Amortization of above and below market rent	(17,078)	(13,847)	(9,890)
Amortization relating to stock based compensation	6,190	4,916	4,684
Provisions for tenant credit losses	1,191	1,805	1,984
Other noncash interest expense	2,139	2,139	2,139
Change in operating assets and liabilities:
Restricted cash	(643)	66	264
Tenant and other receivables	(2,452)	(4,412)	(2,599)
Prepaid expenses	464	(1,363)	501
Accounts payable and accrued expenses	456	4,417	512
Other assets and liabilities, net	3,234	(1,356)	(2,376)
Net cash provided by operating activities	128,295	114,682	86,917
CASH FLOWS FROM INVESTING ACTIVITIES
Investments in real estate	(263,366)	(284,867)	(313,623)
Increase in restricted cash	(844)	35	23
Improvements to properties	(54,097)	(40,758)	(27,515)
Deposits on real estate acquisitions, net	(500)	500	4,000
Net cash used in investing activities	(322,607)	(325,090)	(337,115)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal repayments on mortgages	(8,848)	(7,816)	(84,308)
Proceeds from new mortgage loan	0	0	35,500
Proceeds from term loan	0	0	300,000
Proceeds from draws on credit facility	327,500	332,500	430,000
Payments on credit facility	(282,000)	(370,000)	(451,000)
Issuance of promissory note receivable	0	0	(6,710)
Proceeds on repayment of promissory note receivable	0	6,710	0
Redemption of OP Units	(150)	(38,820)	0
Distributions to OP Unitholders	(91,646)	(84,035)	(68,601)
Deferred financing and other costs	(3,845)	(266)	(1,849)
Proceeds from the issuance of OP Units in connection with issuance of common stock	4,481	184,881	101,293
Registration expenditures	(1,225)	(7,097)	(4,739)
Shares withheld for employee taxes	(1,571)	(1,368)	(1,317)
Net cash provided by financing activities	192,740	214,689	248,269
Net (decrease) increase in cash and cash equivalents	(1,572)	4,281	(1,929)
Cash and cash equivalents at beginning of period	13,125	8,844	10,773
Cash and cash equivalents at end of period	11,553	13,125	8,844
Supplemental disclosure of cash activities:
Cash paid on gross receipts and income for federal and state purposes	253	206	241
Interest paid	46,271	34,275	31,996
Other non-cash investing and financing activities:
Issuance of OP Units in connection with acquisitions	49,599	46,140	150,315
Fair value of assumed mortgages upon acquisition	46,034	17,618	19,024
Intangible lease liabilities	45,456	32,615	37,480
Interest rate swap asset	3,446	875	0
Accrued real estate improvement costs	383	601	590
Equity redemption of OP Units	50,155	15,990	3,184
Senior Notes Due 2027
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of senior notes	250,000	0	0
Senior Notes Due 2026
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of senior notes	0	200,000	0
Senior Notes | Senior Notes Due 2027 | Retail Opportunity Investments Partnership L.P.
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of senior notes	250,000	0	0
Senior Notes | Senior Notes Due 2026 | Retail Opportunity Investments Partnership L.P.
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of senior notes	$ 0	$ 200,000	$ 0