Organization (Narrative) (Details)	9 Months Ended
Sep. 30, 2011 years sqft	Sep. 30, 2010
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership	88.00%	86.20%
Restriction on redemption of OP units from date of issuance (years)	1
One OP unit is equivalent to one share of Common Stock	1
Number of series of preferred units outstanding	1
OP unit conversion rate	1
Number of vehicles in structured parking	43,899
Area of parking in square feet	14,800,000
Area of undeveloped land parcels owned in acres	510.5
Value-added fund institutional investors	2
Commercial Real Estate Properties [Member]
Real Estate Properties [Line Items]
Square footage of real estate property	42,300,000
Number of real estate properties	153
Total Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	147
Total Properties Under Construction [Member]
Real Estate Properties [Line Items]
Square footage of real estate property	2,900,000
Number of real estate properties	7
Office Properties Under Construction [Member]
Real Estate Properties [Line Items]
Number of real estate properties	7
Class A Office Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	128
Office/Technical Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	19
Hotel Property [Member]
Real Estate Properties [Line Items]
Number of real estate properties	1
Retail Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	3
Residential Properties [Member]
Real Estate Properties [Line Items]
Number of real estate properties	2
Investments Through The Value-Added Fund [Member]
Real Estate Properties [Line Items]
Number of real estate properties	24

Area Of Undeveloped Land

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Common Stock Conversion Rate

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Number Of Series Of Preferred Units Outstanding.

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OP Unit Conversion Rate.

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- Definition

Restriction On Redemption Of OP Units From Date Of Issuance In Years

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- Definition

Square Feet For Parking

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- Definition

Value Added Fund Institutional Investors

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- Definition

Vehicles In Structured Parking

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- Definition

The number of units or percentage investment held by the managing member or general partner of the LLC or LP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Practice Bulletin (PB)

-Number 14

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

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- Definition

The number of real estate properties owned as of the balance sheet date.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The amount of square footage related to a real estate property.

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