Real Estate Investments Land, buildings, and improvements (Details) - Parent Company [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Land	$ 4,240,213	$ 4,235,032
Land Improvements	596,729	556,140
Buildings	5,088,332	4,999,378
Building improvements	843,105	787,880
Property, Plant and Equipment, Gross	$ 10,768,379	$ 10,578,430