Capital of the Operating Partnership (Details) - USD ($)		9 Months Ended	12 Months Ended
		Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capital of the Operating Partnership [Line Items]
Units outstanding (in shares)			120,969,823
Ownership interest (in percentage)			90.30%
Shares outstanding (in shares)			109,301,762	99,531,034
Cash redemption of OP Units (in shares)			1,133,550
ROIC common stock (in shares)			755,762
Equity redemption of OP Units, cash (in shares)			377,788
OP Units
Capital of the Operating Partnership [Line Items]
Non-controlling interest redemption value (in usd per share)			$ 20.76
Non-controlling interest redemption value			$ 242,200,000
Common Stock
Capital of the Operating Partnership [Line Items]
Shares outstanding (in shares)			109,301,762	99,531,034	92,991,333	72,445,767
ROIC common stock (in shares)			755,762	174,959
Bellevue Marketplace | OP Units Classified as Mezzanine Equity
Capital of the Operating Partnership [Line Items]
Temporary Equity, Shares Issued				1,946,483
Redeemable OP unit redemption (in shares)			$ 1,828,825
Non-controlling interest redemption value (in usd per share)			$ 17.30
Payments for redemption of redeemable OP units (usd per share)			$ 31,600,000.0
Temporary equity transferred to permanent equity (in shares)		117,658
Retail Opportunity Investments Partnership L.P. | Limited Partner’s Capital
Capital of the Operating Partnership [Line Items]
Remaining units outstanding ( in shares)	[1]		11,668,061	12,195,603	3,921,314	3,132,042
Cash redemption of OP Units (in shares)	[1]		2,206,613	174,959	200,000
ROIC common stock (in shares)	[1]		(755,762)

[1] Consists of limited partnership interests held by third parties.