Segment Reporting (Reportable Segments Consolidated Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Total Assets	$ 7,139,909	$ 7,754,839
Corporate, Non-Segment [Member]
Total Assets	767,307	365,030
Operating Segments [Member]
Total Assets	6,372,602	7,389,809
Operating Segments [Member] | Industrial [Member]
Total Assets	4,501,662	4,677,047
Operating Segments [Member] | Medical Office [Member]
Total Assets	1,247,196	1,229,632
Operating Segments [Member] | Office [Member]
Total Assets	483,641	1,252,627
Operating Segments [Member] | All Other Segments [Member]
Total Assets	0	71,741
Operating Segments [Member] | Service Operations [Member]
Total Assets	$ 140,103	$ 158,762