Organization and Basis of Presentation (Tables)

3 Months Ended

Mar. 31, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of real estate properties

Our stabilized portfolio of operating properties was comprised of the following office properties at March 31, 2013:

	Number of Buildings	Rentable Square Feet	Number of Tenants	Percentage Occupied
Office Properties	116	13,570,059	553	90.3	%

Our stabilized portfolio includes all of our properties with the exception of undeveloped land, development and redevelopment properties currently under construction or committed for construction, "lease-up" properties and properties held-for-sale. We define redevelopment properties as those projects for which we expect to spend significant development and construction costs on existing or acquired buildings pursuant to a formal plan, the intended result of which is a higher economic return on the property. We define "lease-up" properties as properties we recently developed or redeveloped that have not yet reached 95% occupancy and are within one year following cessation of major construction activities. As of March 31, 2013, the following properties were excluded from our stabilized portfolio:

	Number of Properties	Estimated Rentable Square Feet
Development properties under construction (1)	4	1,416,000
Lease-up properties	2	508,000

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(1) Estimated rentable square feet upon completion.