Real Estate Investments - Gross Carrying Value of Properties (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment, Gross [Abstract]
Land		$ 462,014	$ 469,522
Tenant improvements		438,695	433,686
Operating properties		3,702,204	3,586,295
Assets held for sale - real estate investments	[1],[2]	5,576	73,591
Total		3,707,780	3,659,886
Building and Improvements [Member]
Property, Plant and Equipment, Gross [Abstract]
Operating properties		$ 2,801,495	$ 2,683,087

[1] As of March 31, 2017, the Company categorized a retail property located in the Other segment as held for sale in accordance with applicable accounting standards for long lived assets. See Note 3, “Real Estate Investments,” for further information.

[2] Real estate investments related to assets held for sale above represents gross real estate assets and does not include accumulated depreciation or other assets on the balance sheet of the property held for sale. See “Held for Sale” below in this Note 3.