Selected Quarterly Financial Data (Unaudited) - Summary Certain Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Jan. 08, 2016	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 Data [Abstract]
Rental revenues		$ 26,516	$ 25,305	$ 24,251	$ 23,283	$ 21,771	$ 21,303	$ 19,908	$ 18,190	$ 99,355	$ 81,172	$ 64,746
General contracting and real estate services revenues		50,475	38,552	33,200	36,803	41,309	53,822	47,066	29,071	159,030	171,268	103,321
Net operating income		19,740	18,393	17,973	17,371	15,819	16,488	15,101	12,702	26,679	26,584	21,379
Net income (1)		5,145	7,946	3,131	26,533	8,443	4,337	10,285	8,118	$ 28,074	$ 19,642	$ 7,691
Net income attributable to stockholders		$ 3,458	$ 5,212	$ 2,034	$ 17,370	$ 5,328	$ 2,688	$ 6,521	$ 5,105
Net income per share: basic and diluted (in dollars per share)		$ 0.09	$ 0.15	$ 0.06	$ 0.57	$ 0.19	$ 0.10	$ 0.25	$ 0.20	$ 0.85	$ 0.75	$ 0.36
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Richmond Tower
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposition of property	$ 26,200				$ 26,200