Real Estate Investments - Gross Carrying Value of Company's Properties (Details) - USD ($) $ in Thousands		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Property, Plant and Equipment, Gross [Abstract]
Land		$ 469,522		$ 513,268
Tenant improvements		433,686		459,952
Operating properties		3,586,295		3,693,000
Assets held for sale - real estate investments	[1],[2]	73,591	[3]	794,588	[3]	$ 27,436
Total		3,659,886		4,487,588
Building and Improvements [Member]
Property, Plant and Equipment, Gross [Abstract]
Operating properties		$ 2,683,087		$ 2,719,780

[1] As of December 31, 2015, 2970 Market Street was classified as held for sale on the consolidated balance sheets. The property was sold on February 5, 2016. See Note 21, "Subsequent Events," for further information. The sale is not classified as a significant disposition under the accounting guidance for discontinued operations.

[2] As of December 31, 2015, the 58 properties associated with the series of related transactions with Och-Ziff Real Estate were classified as held for sale on the consolidated balance sheets. On February 4, 2016, the Company completed a series of transactions, resulting in the disposition of the properties. See Note 3, “Real Estate Investments,” for further information regarding the disposition. Additionally, as of December 31, 2016, the Company categorized three office properties located in the Metropolitan Washington, D.C. segment and two properties 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.

[3] 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 sheets of the properties held for sale. See Held for Sale section below.