Unsecured Debt (Details Textual) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended		6 Months Ended	3 Months Ended		6 Months Ended																	6 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	Jun. 30, 2011 Unsecured Commercial Bank Credit Facility [Member]	Dec. 31, 2010 Unsecured Commercial Bank Credit Facility [Member]	Jun. 30, 2011 3.63% Convertible Senior Notes due September 2011 [Member]	Jun. 30, 2011 3.625% Convertible Senior Notes due September 2011 and 4% Convertible Senior Notes due December 2035 [Member]	Jun. 30, 2010 3.625% Convertible Senior Notes due September 2011 and 4% Convertible Senior Notes due December 2035 [Member]	Jun. 30, 2011 3.625% Convertible Senior Notes due September 2011 and 4% Convertible Senior Notes due December 2035 [Member]	Jun. 30, 2010 3.625% Convertible Senior Notes due September 2011 and 4% Convertible Senior Notes due December 2035 [Member]	Jun. 30, 2011 3.625% Convertible Senior Notes due September 2011 [Member]	Dec. 31, 2010 3.625% Convertible Senior Notes due September 2011 [Member]	Jun. 30, 2011 5.00% Medium-Term Notes due January 2012 [Member]	Dec. 31, 2010 5.00% Medium-Term Notes due January 2012 [Member]	Jun. 30, 2011 2.95% Term Notes due December 2013 [Member]	Dec. 31, 2010 2.95% Term Notes due December 2013 [Member]	Jun. 30, 2011 6.05% Medium-Term Notes due June 2013 [Member]	Dec. 31, 2010 6.05% Medium-Term Notes due June 2013 [Member]	Jun. 30, 2011 5.13% Medium-Term Notes due January 2014 [Member]	Dec. 31, 2010 5.13% Medium-Term Notes due January 2014 [Member]	Jun. 30, 2011 5.50% Medium-Term Notes due April 2014 [Member]	Dec. 31, 2010 5.50% Medium-Term Notes due April 2014 [Member]	Jun. 30, 2011 5.25% Medium-Term Notes due January 2015 [Member]	Dec. 31, 2010 5.25% Medium-Term Notes due January 2015 [Member]	Mar. 31, 2010 5.25% Medium-Term Notes due January 2015 [Member]	Jun. 30, 2011 5.25% Medium-Term Notes due January 2015 [Member] Variable Rate Debt [Member]	Jun. 30, 2011 5.25% Medium-Term Notes due January 2016 [Member]	Dec. 31, 2010 5.25% Medium-Term Notes due January 2016 [Member]	Jun. 30, 2011 2.27% Term Notes due January 2016 [Member]	Dec. 31, 2010 2.27% Term Notes due January 2016 [Member]	Jun. 30, 2011 3.48% Term Notes due January 2016 [Member]	Mar. 31, 2011 3.48% Term Notes due January 2016 [Member]	Dec. 31, 2010 3.48% Term Notes due January 2016 [Member]	Jun. 30, 2011 8.50% Debentures due September 2024 [Member]	Dec. 31, 2010 8.50% Debentures due September 2024 [Member]	Mar. 31, 2011 4.00% Convertible Senior Notes due December 2035 [Member]	Jun. 30, 2011 4.00% Convertible Senior Notes due December 2035 [Member]	Dec. 31, 2010 4.00% Convertible Senior Notes due December 2035 [Member]	Jun. 30, 2011 4.25% Medium-Term Notes due June 2018 [Member]	May 03, 2011 4.25% Medium-Term Notes due June 2018 [Member]	Dec. 31, 2010 4.25% Medium-Term Notes due June 2018 [Member]	Jun. 30, 2011 4.25% Medium-Term Notes due June 2018 [Member] Variable Rate Debt [Member]	Jun. 30, 2011 Variable Rate Debt [Member]
Line of Credit Facility [Line Items]
Total revolving credit facility,	$ 1,400,000,000		$ 1,400,000,000			$ 600,000,000	$ 600,000,000
Increase in maximum borrowing capacity of unsecured revolving credit facility						750,000,000
Credit facility interest rate						LIBOR plus 47.5 basis points
Description of unsecured credit facility						up to 50% of the commitment and the company can bid out the entire unsecured credit facility once per quarter so long as the company maintain an investment grade rating
Unsecured Debt Instrument (Textuals) [Abstract]
Period of conversion of notes, description								30 days
Principal amount of notes to be considered for conversion								1,000																															1,000
Shares of the company's common stock for each $1,000 principal amount of notes								26.6326																															38.8650
Initial conversion price of notes								$ 37.55																														$ 25.73
Interest rate						0.80%	0.90%
Effect of certain change in control transactions								100.00%
Purchased capped call option								6,700,000
Purchased capped call option strike price								37.548
Written call option with a strike price								43.806
Capped call conversion price								$ 43.806
Amortization of remaining financing costs																																						3,000,000
Remaining financing costs	24,747,000		24,747,000		27,267,000
Debt instrument hedged under interest rate swap agreement																																		150,000,000
Conversion premium percentage of purchased capped call								40.00%
Net cost of approximately of capped call transaction included in stockholder's equity								12,600,000
Weighted Average Interest Rate			4.22%																									5.25%																4.25%	1.58%
Term Notes carried by the company	1,702,185,000		1,702,185,000		1,572,084,000								96,680,000	95,961,000	100,000,000	100,000,000	100,000,000	100,000,000	122,500,000	122,500,000	184,000,000	184,000,000	128,308,000	128,274,000	324,721,000	324,656,000			83,260,000	83,260,000	0	150,000,000	250,000,000		100,000,000	15,644,000	15,644,000		0	167,750,000	297,035,000		0
Fixed interest rate	3.625%		3.625%										3.625%		5.00%		2.95%		6.05%		5.13%		5.50%		5.25%				5.25%		2.27%		3.48%			8.50%			4.00%		4.25%
Notional value of retired debt																																						10,800,000
Write off of unamortized financing costs																																						207,000
Gain(loss) on debt retirement	(40,000)	(1,030,000)	(4,059,000)	(1,030,000)
Notes issued																											150,000,000															300,000,000
Percentage of price of Medium-Term Notes issued																									99.46%																98.988%
Unamortized discount for Medium-Term Notes																																									3,000,000
Interest expense due to adoption of new guidance "net settlement feature"	359,000	928,000	719,000	1,895,000					359,000	928,000	718,000	1,900,000
Unamortized discount	21,500,000		21,500,000		694,000								419,000	1,138,000									192,000	226,000	455,000	519,000															2,965,000
Unsecured Debt (Textuals) [Abstract]
Redeem terms of note			UDR will have the right to redeem the 4.00% notes in whole or in part, at any time or from time to time, for cash equal to 100% of the principal amount of the notes to be redeemed plus any accrued and unpaid interest.
Percentage debt instrument convertible terms of repurchase feature			4.00%
Percentage cash equal to principal amount of the notes			100.00%
Line of Credit	$ 1,700,000		$ 1,700,000
Interest rate of Convertible Senior Notes due Sept. 2011	3.625%		3.625%										3.625%		5.00%		2.95%		6.05%		5.13%		5.50%		5.25%				5.25%		2.27%		3.48%			8.50%			4.00%		4.25%