Capital Structure (UNITED DOMINION REALTY, L.P.) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2014	Dec. 31, 2013
Limited Partners' Capital Account [Line Items]
General Partnership units outstanding	174,111,227
Redeemable noncontrolling interests in the Operating Partnership	$ 249,814	$ 217,597
United Dominion Reality L.P. [Member]
Limited Partners' Capital Account [Line Items]
General Partnership units outstanding	110,883	110,883
Limited partnership units owned	183,167,815	183,167,815
Limited Partners' Capital Account, Required Period To Be Outstanding Before Unit is Redeemable	1 year
UDR, Inc. [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	174,000,344	173,848,891
Percentage of units	95.00%	94.90%
Non-affiliated Partners [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	9,167,471	9,318,924
Percentage of units	5.00%	5.10%
Class A Limited Partner [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned		1,751,671
Cumulative, annual, non-compounded preferred return on Class A Partnership units	8.00%
Value of Class A Partnership units (in dollars per unit)	16.61
Class A Limited Partner [Member] \| United Dominion Reality L.P. [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	1,873,332	1,751,671
Class A Limited Partner [Member] \| UDR, Inc. [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	121,661
Class A Limited Partner [Member] \| Non-affiliated Partners [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	1,751,671

Limited Partners' Capital Account, Required Period To Be Outstanding Before Unit is Redeemable

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- Definition

Cumulative, annual, non-compounded preferred return percentage of Class A Partnership units.

+ References

No definition available.

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- Definition

Limited Partners Capital Account Units Outstanding Percentage.

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- Definition

Value per Class A Partnership unit which preferred return percentage is based.

+ References

No definition available.

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- Definition

The number of general partner units outstanding.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-Subparagraph (SAB TOPIC 4.F)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section F

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- Definition

The number of limited partner units outstanding.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

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-Name Accounting Standards Codification

-Topic 505

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-Paragraph 5

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- Definition

As of the reporting date, the carrying amount of noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. The noncontrolling interest holder's ownership (or holders' ownership) may be in the form of common shares (regardless of class), limited partnership units (regardless of class), non-preferential membership interests, or any other form of common equity regardless of investee entity legal form.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Section S99

-Paragraph 3A

-Subparagraph 14

-URI http://asc.fasb.org/extlink&oid=27011957&loc=SL6540498-122764

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-Topic 480

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