Reportable Segments (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Dec. 31, 2009
Reportable apartment home segment rental income
Total segment and consolidated rental income	$ 177,218,000	$ 153,921,000	$ 347,720,000	$ 305,550,000
Reportable apartment home segment NOI
Total segment and consolidated NOI	118,070,000	100,254,000	228,867,000	198,277,000
Reconciling items:
Non-property income	2,855,000	2,056,000	7,391,000	5,376,000
Property management	(4,873,000)	(4,233,000)	(9,562,000)	(8,403,000)
Other operating expenses	(1,544,000)	(1,457,000)	(3,001,000)	(2,942,000)
Depreciation and amortization	(91,161,000)	(73,726,000)	(175,276,000)	(145,933,000)
Interest	(37,844,000)	(37,945,000)	(78,563,000)	(74,811,000)
General and administrative	(12,918,000)	(10,293,000)	(23,593,000)	(19,933,000)
Other depreciation and amortization	(986,000)	(1,308,000)	(2,029,000)	(2,531,000)
Loss from unconsolidated entities	(1,348,000)	(1,185,000)	(2,680,000)	(1,922,000)
Net (income)/loss attributable to redeemable non-controlling interests in OP	(221,000)	1,064,000	611,000	2,069,000
Non-controlling interests	(37,000)	(45,000)	(88,000)	(80,000)
Net gain on sale of depreciable property	44,658,000	197,000	44,699,000	156,000
Net income/(loss) attributable to UDR, Inc.	14,651,000	(26,621,000)	(13,224,000)	(50,677,000)
Reportable apartment home segment assets:
Total segment assets	7,298,806,000		7,298,806,000		6,881,347,000
Accumulated depreciation	(1,726,258,000)		(1,726,258,000)		(1,638,326,000)
Total segment assets - net book value	5,572,548,000		5,572,548,000		5,243,021,000
Reconciling items:
Cash and cash equivalents	21,634,000	8,074,000	21,634,000	8,074,000	9,486,000	5,985,000
Marketable securities	0		0		3,866,000
Restricted cash	20,220,000		20,220,000		15,447,000
Deferred financing costs, net	24,747,000		24,747,000		27,267,000
Notes receivable	7,800,000		7,800,000		7,800,000
Investment in unconsolidated joint ventures	177,404,000		177,404,000		148,057,000
Other assets	137,424,000		137,424,000		74,596,000
Total assets	5,961,777,000		5,961,777,000		5,529,540,000
Reportable Segments Additional (Textuals) [Abstract]
Capital expenditures related to segments	12,500,000	13,800,000	20,500,000	22,100,000
Reportable Segment (Textuals) [Abstract]
Condition for Community considered to have stabilized occupancy			90% occupancy for at least three consecutive months
Tenant or related group of tenants contributed 10% or more of company total revenue	0	0	0	0
Same Communities Western Region [Member]
Reportable apartment home segment rental income
Total segment and consolidated rental income	54,323,000	52,432,000	107,459,000	104,404,000
Reportable apartment home segment NOI
Total segment and consolidated NOI	38,078,000	36,216,000	74,339,000	71,764,000
Reportable apartment home segment assets:
Total segment assets	2,317,600,000		2,317,600,000		2,308,491,000
Same Communities Mid-Atlantic Region [Member]
Reportable apartment home segment rental income
Total segment and consolidated rental income	39,105,000	37,622,000	77,547,000	74,636,000
Reportable apartment home segment NOI
Total segment and consolidated NOI	26,883,000	25,820,000	53,049,000	50,667,000
Reportable apartment home segment assets:
Total segment assets	1,269,193,000		1,269,193,000		1,264,314,000
Same Communities Southeastern Region [Member]
Reportable apartment home segment rental income
Total segment and consolidated rental income	32,468,000	31,484,000	64,664,000	62,991,000
Reportable apartment home segment NOI
Total segment and consolidated NOI	20,167,000	19,359,000	40,280,000	39,030,000
Reportable apartment home segment assets:
Total segment assets	1,059,639,000		1,059,639,000		1,054,130,000
Same Communities Southwestern Region [Member]
Reportable apartment home segment rental income
Total segment and consolidated rental income	15,196,000	14,696,000	30,249,000	29,454,000
Reportable apartment home segment NOI
Total segment and consolidated NOI	9,402,000	8,585,000	18,250,000	17,430,000
Reportable apartment home segment assets:
Total segment assets	555,424,000		555,424,000		553,176,000
Non-Mature communities/Other [Member]
Reportable apartment home segment rental income
Total segment and consolidated rental income	36,126,000	17,687,000	67,801,000	34,065,000
Reportable apartment home segment NOI
Total segment and consolidated NOI	23,540,000	10,274,000	42,949,000	19,386,000
Reportable apartment home segment assets:
Total segment assets	2,096,950,000		2,096,950,000		1,701,236,000
Reportable Segments Additional (Textuals) [Abstract]
Capital expenditures related to segments	$ 1,200,000	$ 1,600,000	$ 2,100,000	$ 2,200,000