Selected Quarterly Financial Data - Summary Certain Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Selected Quarterly Financial Data
Rental revenues	$ 21,771	$ 21,303	$ 19,908	$ 18,190	$ 17,521	$ 16,713	$ 15,319	$ 15,193	$ 81,172	$ 64,746	$ 57,520
General contracting and real estate services revenues	41,309	53,822	47,066	29,071	32,060	31,532	20,495	19,234	171,268	103,321	82,516
Net operating income	15,819	16,488	15,101	12,702	12,685	11,883	11,212	11,123	26,584	21,379	19,659
Net income	8,443	4,337	10,285	8,118	5,226	2,754	2,273	2,506	$ 19,642	$ 7,691	$ 7,336
Net income attributable to stockholders	$ 5,328	$ 2,688	$ 6,521	$ 5,105	$ 3,286	$ 1,615	$ 1,325	$ 1,465
Net income per share: basic and diluted	$ 0.19	$ 0.10	$ 0.25	$ 0.20	$ 0.13	$ 0.08	$ 0.07	$ 0.08	$ 0.75	$ 0.36	$ 0.39