Income/(Loss) Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income/(loss) from continuing operations attributable to common stockholders																	$ 0.59	$ (0.01)	$ (0.22)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	$ 6,485		$ 10,611		$ 4,359		$ (5,195)		$ (3,374)		$ 2,351		$ 4,525		$ (1,162)		$ 16,260	$ 2,340	$ (46,305)
Gain/(loss) on sales of real estate owned, net of tax																	143,572	0	0
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest																	(5,511)	48	2,089
Income (Loss) from Continuing Operations Attributable to Parent																	154,324	2,448	(44,356)
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest																	3	60	(140)
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest																	5,511	1,530	7,986
Net (loss)/income attributable to common stockholders	64,486		39,618		29,076		17,430		35,769		2,257		4,261		(1,199)		150,610	41,088	203,376
Net income/(loss)																	159,842	46,282	220,303
Premium on preferred stock redemption or repurchases, net																	0	0	(2,791)
udr_IncomeLossContinuingOperationsAvailableToCommonShareholders																	150,600	(1,276)	(53,157)
Income/(loss) from discontinued operations, net of tax	0		79		18		(87)		41,376		884		829		853		10	43,942	266,608
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest																	0	(1,578)	(10,075)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent																	10	42,364	256,533
Weighted Average Number of Shares Issued, Basic																	252,707	250,684	239,482
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units																	(1,179)	(715)	(631)
Weighted Average Number of Shares Outstanding, Basic and Diluted																	251,528	249,969	238,851
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic and Diluted Share																	$ 0.00	$ 0.17	$ 1.07
Net income/(loss) attributable to common stockholders — basic and diluted (in dollars per share)	$ 0.25	[1]	$ 0.16	[1]	$ 0.12	[1]	$ 0.07	[1]	$ 0.14	[1]	$ 0.01	[1]	$ 0.02	[1]	$ 0.00	[1]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements																	1,917	0	0
Weighted average number of common shares outstanding — diluted	256,000		253,732		252,191		251,822		249,987		251,454		251,406		249,917		253,445	249,969	238,851
Income/(loss) from discontinued operations attributable to common stockholders																	$ 0.00	$ 0.17	$ 1.07
Earnings Per Share, Diluted																	$ 0.59	$ 0.16	$ 0.85
Noncontrolling Interest
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest																	3	60	(140)
Series G Preferred Stock [Member]
Dividends, Preferred Stock																	0	0	(2,286)
Series E Preferred Stock [Member]
Dividends, Preferred Stock																	$ (3,724)	$ (3,724)	$ (3,724)

[1] Quarterly income/(loss) per share amounts may not total to the annual amounts.