Summary of Significant Accounting Policies Change in Accounting Principle (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred financing and leasing costs, net	$ 192,109	$ 192,764
Mortgage loans, net	307,908	484,852
Unsecured notes, net	2,580,108	2,498,021
Adjustments for New Accounting Principle, Early Adoption [Member] | Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred financing and leasing costs, net	206,327	206,286
Mortgage loans, net	309,711	487,301
Unsecured notes, net	2,592,523	2,509,094
New Accounting Pronouncement, Early Adoption, Effect [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred financing and leasing costs, net	(14,218)	(13,522)
Mortgage loans, net	(1,803)	(2,449)
Unsecured notes, net	$ (12,415)	$ (11,073)