Investments in Unconsolidated Joint Ventures - Narrative (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014 office_properties office_buildings sqft jointventure	Dec. 31, 2013
Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Number of Joint Venture	4
Number of properties held by unconsolidated joint ventures	6
Number of office buildings held by unconsolidated joint ventures	12
Rentable square feet held by unconsolidated joint ventures (in square feet)	1,100,000
JV Basis Differential	$ (0.1)	$ (0.1)
Unconsolidated Properties | Minimum
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint venture ownership interest percentage	5.00%
Unconsolidated Properties | Maximum
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint venture ownership interest percentage	32.20%
Unconsolidated Properties with Managing Ownership Interests
Schedule of Equity Method Investments [Line Items]
Number of Joint Venture	1