Commitments to Acquire/Dispose of Real Estate (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Land Parcels Contracted to be Acquired	3
Units Contracted To Be Acquired	0
Equity Method Investment, Ownership Percentage	20.00%
Commitments to Acquire Real Estate
Properties Acquired-Total	0
Purchase Price - Total	$ 45,500
Commitments to Dispose of Real Estate
Properties Disposed - Total	50
Rental Units Disposed-Total	13,772
Sales price-Rental Properties	2,012,960
Land Parcels Contracted to be Disposed	1
Land Parcel [Member]
Land Parcels Contracted to be Acquired	0
Units Contracted To Be Acquired	0
Commitments to Acquire Real Estate
Purchase Price - Total	45,500
Archstone [Member]
Land Parcels Contracted to be Acquired	4
Equity Method Investment, Ownership Percentage	60.00%
Commitments to Acquire Real Estate
Properties Acquired-Total	75
Purchase Price - Total	8,900,000
Rental Properties Disposed of [Member]
Commitments to Dispose of Real Estate
Properties Disposed - Total	50
Rental Units Disposed-Total	13,772
Sales price-Rental Properties	$ 1,983,960
Land Parcel [Member]
Commitments to Dispose of Real Estate
Rental Units Disposed-Total	0
Land Parcels Contracted to be Disposed	0

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- Definition

Total number of land parcels to be acquired subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Land Parcels Contracted to be Disposed

+ References

No definition available.

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- Definition

Total number of rental properties to be acquired subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Total number of rental properties to be disposed of subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

The amount of the fixed and determinable portion of an unrecorded purchase commitment for the acquisition of a rental property or land parcel subsequent to the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

The amount of the fixed and determinable portion of an unrecorded sales commitment for the disposition of a rental property or land parcel subsequent to the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Total number of rental units to be acquired subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Total number of rental units to be disposed of subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ References

No definition available.

+ Details

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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)

-Number 159

-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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-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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