Company's Joint Venture Ownership Percentage

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- Definition

Disposition price.

+ References

No definition available.

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- Definition

Fixed Price Option Expiration Date

+ References

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- Definition

Future Fixed Price To Acquire Remaining Portion Of Joint Venture

+ References

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- Definition

Number of floors of real estate

+ References

No definition available.

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- Definition

Partner's Joint Venture Ownership Percentage

+ References

No definition available.

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- Definition

Area of a real estate property.

+ References

No definition available.

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- Definition

Amount of cash paid to acquire the entity.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 51

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-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.

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- Definition

Amount of acquisition cost of a business combination allocated to land included in real estate.

+ References

No definition available.

+ Details

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

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- Definition

Interest rate stated in the contractual debt agreement.

+ References

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Article 5

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-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.

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- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

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-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.

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- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 18

-Subparagraph f

-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.

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-Topic 323

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-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.

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- Definition

Net rentable area for properties owned.

+ References

No definition available.

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- Definition

The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

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

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Subsequent Events (Detail) (USD $)	1 Months Ended			1 Months Ended			1 Months Ended	0 Months Ended
Subsequent Events (Detail) (USD $)	Sep. 17, 2012	Nov. 08, 2012 Subsequent Event [Member]	Oct. 01, 2012 Subsequent Event [Member] 500 North Capitol Street, NW [Member] sqft	Oct. 04, 2012 Subsequent Event [Member] Fountain Square [Member] sqft	Oct. 04, 2012 Subsequent Event [Member] Fountain Square [Member] Class A Office Properties [ Member] sqft	Oct. 04, 2012 Subsequent Event [Member] Fountain Square [Member] Retail Properties [ Member] sqft	Oct. 19, 2012 Subsequent Event [Member] Pursuit of Transbay Tower [Member] Floors sqft	Oct. 29, 2012 Subsequent Event [Member] One Sixty Four Lexington Road [Member] sqft
Ownership percentage			30.00%
Net rentable area			232,000	764,000	522,000	242,000		64,000
Acquisition aggregate purchase price				$ 385,000,000
Mortgage loan on acquisition of property				211,300,000
Company's joint venture ownership percentage				50.00%			50.00%
Interest on mortgage loan paid in cash				87,000,000
Partner's joint venture ownership percentage				50.00%
Mortgage loan interest rate				5.71%
Mortgage loan maturity date				Oct. 11, 2016
Partner's interest acquisition price				102,000,000
Fixed price option rights expiry date				Jan. 31, 2016
Number of floors of real estate							61
Area of real estate property							1,400,000
Purchase price of land							190,000,000
Sale of property, agreement price								$ 3,200,000
Common stock dividend declared	$ 0.55	$ 0.65
Dividends payable date		Jan. 29, 2013
Dividends record date		Dec. 31, 2012