Common Stock of ROIC (Details Textual)		6 Months Ended		21 Months Ended
	Sep. 19, 2014 USD ($) agreement $ / shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2015 $ / shares	Jul. 31, 2013 USD ($)
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares		$ 0.0001		$ 0.0001	$ 0.0001
Proceeds from the sale of common stock		$ 39,964,000	$ 9,936,000
Registration expenditures		$ 626,000	$ 325,000
Stock repurchase program, authorized amount						$ 50,000,000.0
Sales Agreement
Class of Stock [Line Items]
Number of sales agreements entered into | agreement	4
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001
Common shares that may be sold under a sales agreement, aggregate offering price, maximum	$ 100,000,000.0
Shares sold during the year (shares) | shares		1,943,059		2,487,626
Proceeds from the sale of common stock		$ 40,000,000		$ 49,900,000
Registration expenditures		$ 524,000		$ 673,000