The amount due to UDR by an equity method investment of the entity.

No definition available.

Name:	udr_EquityMethodInvestmentSummarizedFinancialInformationAmountDueToRelatedParty
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of debt due to third parties by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	udr_EquityMethodInvestmentSummarizedFinancialInformationAmountOfDebtDueToThirdParties
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstract
Namespace Prefix:	udr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of depreciation and amortization reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	udr_EquityMethodInvestmentSummarizedFinancialInformationDepreciationAmortization
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of net real estate assets reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	udr_EquityMethodInvestmentSummarizedFinancialInformationRealEstateNet
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Investment In and Advances to Unconsolidated Joint Ventures, Net

+ References

No definition available.

+ Details

Name:	udr_InvestmentInAndAdvancesToUnconsolidatedJointVenturesNet
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 40

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.U.Q2)

-URI http://asc.fasb.org/extlink&oid=6955272&loc=d3e221323-122791

+ Details

Name:	us-gaap_DeferredGainOnSaleOfProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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.

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570

+ Details

Name:	us-gaap_EquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of assets reported by an equity method investment of the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (c)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(g))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph g

-Subparagraph 1, 2

-Article 4

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph w

-Article 1

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-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.

Reference 8: 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 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph bb

-Article 1

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of equity, including noncontrolling interest, reported by an equity method investment of the entity.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-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.

Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 26

-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.

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationIncomeStatementAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of liabilities reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of equity attributable to noncontrolling interests of an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationMinorityInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of net income (loss) reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

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

-Subparagraph (b)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 9

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph b

-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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 19

-Subparagraph c

-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 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.12)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 7

+ Details

Name:	us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Joint Ventures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Financial information relating to unconsolidated joint ventures operations
UDR recorded loss from unconsolidated entities	$ 515	$ (2,412)	$ (2,287)	$ (5,103)
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	558,804		558,804		507,037
Deferred fees and gains on the sale of depreciable property	(25,469)	(29,406)	(25,469)	(29,406)
Investment in and advances to unconsolidated joint ventures, net	533,335		533,335		477,631
Unconsolidated Joint Ventures [Member]
Financial information relating to unconsolidated joint ventures operations
Revenues	62,607	74,725	123,687	137,750
Real estate depreciation and amortization	21,336	26,489	43,114	52,374
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	23,642	3,544	27,479	(5,077)
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	3,235,228		3,235,228		3,189,814
Total assets	3,303,195		3,303,195		3,266,518
Amount due to UDR	32,731		32,731		34,843
Third party debt	1,773,283		1,773,283		1,663,427
Total liabilities	1,846,961		1,846,961		1,747,855
Total equity	1,456,234		1,456,234		1,518,663
Equity held by non-controlling interest	0		0		12,755
Unconsolidated Joint Venture Vitruvian Park [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Ownership percentage, equity method investment	50.00%		50.00%
Operating Community [Member] \| Unconsolidated Joint Venture UDR Met Life I Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	52,455		52,455		75,129
Ownership percentage, equity method investment	13.20%		13.20%
Number of apartment homes	1,641		1,641
Joint Venture and Partnership Number of Operating Communities Owned	8		8
Operating Community [Member] \| Unconsolidated Joint Venture UDR MetLife II Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	323,401		323,401		327,001
Ownership percentage, equity method investment	50.00%		50.00%
Number of apartment homes	3,119		3,119
Joint Venture and Partnership Number of Operating Communities Owned	15		15
Operating Community [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	80,162		80,162		0
Ownership percentage, equity method investment	50.00%		50.00%
Number of apartment homes	739		739
Joint Venture and Partnership Number of Operating Communities Owned	2		2
Operating Community [Member] \| Unconsolidated Joint Venture Two Stoughton Massachusetts [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	16,020		16,020		16,311
Ownership percentage, equity method investment	95.00%		95.00%
Number of apartment homes	240		240
Joint Venture and Partnership Number of Operating Communities Owned	1		1
Operating Community [Member] \| Unconsolidated Joint Venture Three [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	27,739		27,739		29,663
Ownership percentage, equity method investment	30.00%		30.00%
Number of apartment homes	660		660
Joint Venture and Partnership Number of Operating Communities Owned	3		3
Operating Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	1,999		1,999		3,457
Ownership percentage, equity method investment	20.00%		20.00%
Number of apartment homes	3,359		3,359
Joint Venture and Partnership Number of Operating Communities Owned	8		8
Development Community [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Number of apartment homes	391		391
Joint Venture and Partnership Number of Operating Communities Owned	1		1
Development Community [Member] \| Unconsolidated Joint Venture Five San Diego California [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	30,920		30,920		29,930
Ownership percentage, equity method investment	95.00%		95.00%
Number of apartment homes	264		264
Joint Venture and Partnership Number of Operating Communities Owned	1		1
Development Community [Member] \| Unconsolidated Joint Venture Six College Park California [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	$ 26,108		$ 26,108		$ 25,546
Ownership percentage, equity method investment	95.00%		95.00%
Number of apartment homes	256		256
Joint Venture and Partnership Number of Operating Communities Owned	1		1
Land [Member] \| Unconsolidated Joint Venture UDR Met Life I Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Ownership percentage, equity method investment	4.30%		4.30%
Joint Venture and Partnership Number of Operating Communities Owned	8		8
Land [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Joint Venture and Partnership Number of Operating Communities Owned	6		6