Joint Ventures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Financial information relating to unconsolidated joint ventures operations
UDR recorded loss from unconsolidated entities	$ (2,802)	$ (2,691)
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	490,776		507,037
Deferred fees and gains on the sale of depreciable property	(29,379)	(29,406)
Investment in and advances to unconsolidated joint ventures, net	461,397		477,631
Unconsolidated Joint Ventures [Member]
Financial information relating to unconsolidated joint ventures operations
Revenues	61,080	63,025
Real estate depreciation and amortization	21,778	25,885
Net loss	3,837	8,621
UDR recorded loss from unconsolidated entities	2,802	2,691
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	3,181,823		3,189,814
Total assets	3,248,847		3,266,518
Amount due to UDR	30,310		34,843
Third party debt	1,676,444		1,663,427
Total liabilities	1,740,604		1,747,855
Total equity	1,508,243		1,518,663
Equity held by non-controlling interest	12,490		12,755
Apartment 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	30,514		29,930
Equity Method Investment, Ownership Percentage	95.00%
Number of Units in Real Estate Property	264
Number of Real Estate Properties	1
Apartment Community [Member] \| Unconsolidated Joint Venture One U D R Met Life Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	75,959		75,129
Equity Method Investment, Ownership Percentage	13.30%
Number of Units in Real Estate Property	2,547
Number of Real Estate Properties	14
Apartment 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	25,930		25,546
Equity Method Investment, Ownership Percentage	95.00%
Number of Units in Real Estate Property	256
Number of Real Estate Properties	1
Apartment Community [Member] \| Unconsolidated Joint Venture Seven UDR MetLife II Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	311,005		327,001
Equity Method Investment, Ownership Percentage	50.00%
Number of Units in Real Estate Property	2,752
Number of Real Estate Properties	13
Apartment Community [Member] \| Unconsolidated Joint Venture Two Stoughton Massachusetts [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	16,162		16,311
Equity Method Investment, Ownership Percentage	95.00%
Number of Units in Real Estate Property	240
Number of Real Estate Properties	1
Apartment Community [Member] \| Unconsolidated Joint Venture Three [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	28,598		29,663
Equity Method Investment, Ownership Percentage	30.00%
Number of Units in Real Estate Property	660
Number of Real Estate Properties	3
Apartment Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in unconsolidated joint ventures	$ 2,608		$ 3,457
Equity Method Investment, Ownership Percentage	20.00%
Number of Units in Real Estate Property	3,359
Number of Real Estate Properties	8
Land [Member] \| Unconsolidated Joint Venture One U D R Met Life Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Equity Method Investment, Ownership Percentage	4.30%
Number of Real Estate Properties	8

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

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

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

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

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Investment In and Advances to Unconsolidated Joint Ventures, Net

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

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

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

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

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

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

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

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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.

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No definition available.

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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.

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

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No definition available.

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

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