Properties, Net (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Properties
Projects in development or held for future development	$ 403,361	$ 403,494
Projects in development or held for future development [Member] | Land [Member]
Properties
Projects in development or held for future development	207,760	240,825
Projects in development or held for future development [Member] | Development in progress, excluding land [Member]
Properties
Projects in development or held for future development	$ 195,601	$ 162,669