The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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- Definition

Carrying amount as of the balance sheet date, net of valuation allowances and impairment losses, of costs of land expected to be developed in the near term plus capitalized costs of development, for purposes of selling completed units to home buyers or commercial or industrial entities..

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 6

-Subparagraph a

-Article 5

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 67

-Paragraph 4, 5, 6, 7

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

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- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6970148&loc=SL6759159-111685

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- Definition

Estimated Development Costs

+ References

No definition available.

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- Definition

Land, Acres Held

+ References

No definition available.

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- Definition

Percentage of capital contribution through debt

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- Definition

Percentage Of Residential Property To Be Leased To Achieve Project Stabilization Stage

+ References

No definition available.

+ Details

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Real Estate Investments Noncontrolling Interests in Subsidiaries (Details) (USD $)	0 Months Ended	12 Months Ended				0 Months Ended		0 Months Ended		1 Months Ended
	Jun. 15, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 4661 Kenmore Avenue [Member] acre	Jun. 15, 2011 Six Fifty North Glebe Road [Member]	Dec. 31, 2011 Six Fifty North Glebe Road [Member]	Nov. 23, 2011 Braddock Gateway [Member]	Dec. 31, 2011 Braddock Gateway [Member]	Oct. 31, 2011 Northern Virginia Industrial Park I I Member
Real Estate Properties [Line Items]
Land, Acres Held					0.8
Estimated Development Costs						$ 43,500,000		$ 95,000,000
Percentage Of Capital Contribution Through Debt	70.00%					70.00%		70.00%
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage						90.00%		95.00%
Percentage Of Residential Property To Be Leased To Achieve Project Stabilization Stage						90.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners						10.00%		5.00%
Inventory, Real Estate, Land and Land Development Costs							13,400,000		14,400,000
Gain (Loss) on Sale of Properties		$ 97,491,000	$ 21,600,000	$ 13,300,000						$ 400,000