Selected Quarterly Financial Data - Summary Certain Selected Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Rental revenues	$ 17,521	$ 16,713	$ 15,319	$ 15,193	$ 14,992	$ 14,899	$ 14,231	$ 13,398	$ 64,746	$ 57,520	$ 54,436
General contracting and real estate services revenues	32,060	31,532	20,495	19,234	19,373	21,896	23,291	17,956	103,321	82,516	54,046
Net operating income	12,685	11,883	11,212	11,123	11,516	10,731	10,372	9,455	21,379	19,659	24,691
Net income	5,226	2,754	2,273	2,506	2,866	1,252	8,404	1,931	7,691	7,336
Net income attributable to stockholders	$ 3,286	$ 1,615	$ 1,325	$ 1,465	$ 1,705	$ 745	$ 4,886
Net income per share: basic and diluted	$ 0.13	$ 0.08	$ 0.07	$ 0.08	$ 0.09	$ 0.04	$ 0.26		$ 0.37	$ 0.39