Quarterly Results of Operations (Unaudited) (Details) - Quarterly Results of Operations for ROIC - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 63,070	$ 59,354	$ 58,671	$ 56,094	$ 51,285	$ 50,077	$ 46,215	$ 45,122	$ 237,189	$ 192,699	$ 155,864
Net income	10,652	8,215	8,638	8,925	7,468	7,837	5,411	4,376	36,430	25,092	21,050
Net income attributable to ROIC	$ 9,621	$ 7,402	$ 7,704	$ 8,027	$ 6,921	$ 7,542	$ 5,201	$ 4,200	$ 32,754	$ 23,864	$ 20,301
Earnings per share/unit - basic and diluted (in usd per share)	$ 0.09	$ 0.07	$ 0.08	$ 0.08	$ 0.07	$ 0.08	$ 0.05	$ 0.04	$ 0.31	$ 0.25	$ 0.24