Joint Ventures (Details Textual) (USD $)	3 Months Ended		6 Months Ended					1 Months Ended					1 Months Ended			1 Months Ended				3 Months Ended	6 Months Ended								6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Nov. 30, 2010	Nov. 30, 2010 Land [Member] Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Nov. 30, 2010 Buildings [Member] Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Nov. 30, 2010 Intangible Assets [Member] Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Mar. 31, 2010 989 Elements [Member]	Jun. 30, 2011 989 Elements [Member]	Dec. 31, 2010 989 Elements [Member]	Mar. 31, 2010 Elements Too [Member]	Jun. 30, 2011 Elements Too [Member]	Dec. 31, 2010 Elements Too [Member]	Mar. 31, 2010 Bellevue [Member]	Jun. 30, 2011 Bellevue [Member]	Dec. 31, 2010 Bellevue [Member]	Nov. 30, 2010 Joint venture one UDR/Met Life Partnership [Member]	Jun. 30, 2011 Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Jun. 30, 2011 Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Dec. 31, 2010 Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Nov. 30, 2010 Unconsolidated Joint Venture One/UDR MetLife Partnership [Member]	Jun. 30, 2011 Unconsolidated Joint Venture Two Stoughton Massachusetts [Member]	Dec. 31, 2010 Unconsolidated Joint Venture Two Stoughton Massachusetts [Member]	Oct. 31, 2010 Unconsolidated Joint Venture Two Stoughton Massachusetts [Member]	Jun. 30, 2011 Unconsolidated Joint Venture Three [Member]	Dec. 31, 2010 Unconsolidated Joint Venture Three [Member]	Jun. 30, 2011 Unconsolidated Joint Venture Four Texas [Member]	Dec. 31, 2010 Unconsolidated Joint Venture Four Texas [Member]	Jun. 30, 2011 Unconsolidated Joint Venture Five San Diego California [Member]	May 31, 2011 Unconsolidated Joint Venture Five San Diego California [Member]	Jun. 30, 2011 Unconsolidated Joint Venture Six College Park Maryland [Member]
Joint Ventures
Agreement to Purchase Interest in Joint Venture										49.00%	98.00%	98.00%	49.00%	98.00%	98.00%	49.00%	98.00%	98.00%
Payments related to the buyout of joint venture				$ 16,141,000						$ 7,700,000			$ 3,200,000			$ 5,200,000
Company's investment in joint venture																				129,500,000	129,500,000	122,200,000		17,200,000	10,300,000		5,000,000	5,200,000	8,500,000	10,300,000	10,300,000		6,900,000
Contribution in Cash and Property Equal to Fair Value of Properties																													20.00%
Loss from unconsolidated entities	(1,348,000)	(1,185,000)	(2,680,000)	(1,922,000)
Equity Method Investment, Ownership Percentage	30.00%		30.00%		30.00%		4.11%													12.27%	12.27%						30.00%
Company's contribution in cash equal to fair value of the properties																													80.00%
Joint Venture, Number of Apartment Homes in Operating Communities											166			274			430		5,748							240	151		3,992			263	256
Number of operating communities in joint venture						26																							10
Number of land parcels owned							10
Number of additional apartment homes							2,000
Initial investment in equity method investment																							100,800,000			10,000,000			20,400,000		9,900,000		7,100,000
Cash paid in partial consideration for acquisition of ownership interest in joint venture																							71,800,000
Payable incurred in partial consideration for acquisition of ownership interest in joint venture																							30,000,000
State principal amount of payable																							30,000,000
Unamortized discount	21,500,000		21,500,000		694,000																		1,000,000
First installment of payable incurred in partial consideration for acquisition of ownership interest in joint venture																							20,000,000
Second installment of payable incurred in partial consideration for acquisition of ownership interest in joint venture																							10,000,000
Net carrying amount of payable incurred in partial consideration for acquisition of ownership interest in joint venture																				29,500,000	29,500,000	29,100,000	29,500,000
Effective interest rate of payable																							2.67%
Interest expense incurred during period																				196,000	391,000
UDR's proportionate share in the underlying net assets of the joint venture																							111,400,000
Indemnification of Hanover's loan guarantees																				333,000,000	333,000,000
Carrying value of loans associated with indemnification																				209,000,000	209,000,000
Number of operating communities of sub-tier partnerships associated with loan indemnification																					26
Anticipated Period to refinance loans by partnership																					12 months
Difference between total cost of the Company's equity investment and proportionate share in the underlying assets of the joint venture							3,900,000	8,400,000	(1,600,000)														10,600,000
Amortization/Accretion of the Company's carrying value of its equity method investment	395,000		791,000
Amortization period attributable to adjustment to UDR's proportionate share in partnership's assets								45 years	11 months
Joint venture investment in multifamily properties																											450,000,000
Total equity contribution by partners when fully invested																											180,000,000
UDR's equity investment in joint venture when fully invested																											54,000,000
Non-controlling interest held in joint venture																								95.00%	95.00%						95.00%		95.00%
Number of properties purchased from UDR																													9
Joint Venture (Textuals) [Abstract]
Total ownership of our consolidated joint ventures	less than 100%		less than 100%
Management fees for our involvement in the joint ventures	2,700,000	689,000	3,900,000	1,100,000
Deferred profit from the sale of properties	$ 29,011,000		$ 29,011,000		$ 28,943,000