Segment Reporting (Reportable Segments Consolidated Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Total Assets	$ 7,114,521	$ 7,754,839
Corporate, Non-Segment [Member]
Total Assets	586,073	365,030
Operating Segments [Member]
Total Assets	6,528,448	7,389,809
Operating Segments [Member] | Industrial [Member]
Total Assets	4,510,800	4,677,047
Operating Segments [Member] | Medical Office [Member]
Total Assets	1,226,567	1,229,632
Operating Segments [Member] | Office [Member]
Total Assets	654,467	1,252,627
Operating Segments [Member] | All Other Segments [Member]
Total Assets	0	71,741
Operating Segments [Member] | Service Operations [Member]
Total Assets	$ 136,614	$ 158,762