Common Stock of ROIC (Narrative) (Details)				12 Months Ended
	Dec. 12, 2017 $ / shares shares	Jul. 12, 2016 USD ($) shares	Sep. 19, 2014 USD ($) agreement $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Oct. 11, 2017 shares	Sep. 08, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jul. 31, 2013 USD ($)
Common Stock and Warrants of ROIC (Details) [Line Items]
Common stock issued (in shares) | shares		6,555,000
Proceeds from the issuance of OP Units in connection with issuance of common stock		$ 133,000,000		$ 4,481,000	$ 184,881,000	$ 101,293,000
Common stock, par value (in usd per share) | $ / shares				$ 0.0001	$ 0.0001
Stock issuance costs				$ 1,225,000	$ 7,097,000	$ 4,739,000
Stock repurchase program, authorized amount										$ 50,000,000.0
Sales Agreement
Common Stock and Warrants of ROIC (Details) [Line Items]
Common stock issued (in shares) | shares				34,001	2,202,254
Proceeds from the issuance of OP Units in connection with issuance of common stock				$ 681,000	$ 45,600,000
Number of sales agreements | agreement			3
Common stock, par value (in usd per share) | $ / shares			$ 0.0001
Common shares that may be sold under a sales agreement aggregate offering price, maximum			$ 100,000,000
Stock issuance costs				9,000	$ 584,000
Revolving Credit Facility
Common Stock and Warrants of ROIC (Details) [Line Items]
Line of credit facility, maximum borrowing capacity								$ 600,000,000	$ 500,000,000
Fullerton Crossroads and Riverstone Marketplace
Common Stock and Warrants of ROIC (Details) [Line Items]
LP capital account, units issued (in shares) | shares							2,405,430
Vancouver, Washington | Fullerton Crossroads and Riverstone Marketplace
Common Stock and Warrants of ROIC (Details) [Line Items]
LP capital account, units issued (in shares) | shares							2,405,430
Common stock issued (in shares) | shares	2,584,254
Share price (usd per share) | $ / shares	$ 21.25
Restricted cash				$ 3,800,000