Joint Ventures (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial information relating to unconsolidated joint ventures operations
Revenues	$ 193,453	$ 142,842	$ 109,412
Real estate depreciation and amortization	69,399	51,830	51,120
Net loss	(42,667)	(36,075)	(3,957)
UDR recorded loss from unconsolidated entities	(7,006)	(415)	(8,579)
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	2,941,803	2,165,667
Total assets	3,219,250	3,198,204
Amount due to UDR	2,997	9,703
Third party debt	1,504,477	1,164,007
Total liabilities	1,781,515	1,776,709
Total equity	1,437,735	1,421,495
Investment in and advances to unconsolidated joint ventures, net	718,226	507,655
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	229,706	577,203
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	216,196	985,408
Property operating expenses	72,099	49,390	34,188
Operating income/(loss)	51,955	41,622	24,104
Interest expense	(58,591)	(45,726)	(35,621)
Other income/(expense)	0	1	(9)
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	(36,031)	(31,972)	7,569
Cash and cash equivalents	32,544	22,546
Other assets	28,707	24,583
Accounts payable and accrued liabilities	44,335	25,796
MetLife I
Financial information relating to unconsolidated joint ventures operations
Revenues	727	691	632
Real estate depreciation and amortization	2,130	115	124
Net loss	(33,823)	(22,433)	8,865
UDR recorded loss from unconsolidated entities	(2,955)	(4,675)	(1,750)
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	89,482	90,971
Total assets	93,297	849,485
Amount due to UDR	107	4,520
Third party debt	0	0
Total liabilities	5,966	351,419
Total equity	87,331	498,066
Investment in and advances to unconsolidated joint ventures, net	13,306	47,497
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	5,110	346,810
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	1,978	753,427
Property operating expenses	618	621	252
Operating income/(loss)	(2,021)	(45)	256
Interest expense	0	0	0
Other income/(expense)	0	0	0
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	(31,802)	(22,388)	8,609
Cash and cash equivalents	1,983	305
Other assets	(146)	4,782
Accounts payable and accrued liabilities	749	89
MetLife II
Financial information relating to unconsolidated joint ventures operations
Revenues	152,047	109,926	87,386
Real estate depreciation and amortization	41,504	30,122	32,553
Net loss	9,900	8,941	(83)
UDR recorded loss from unconsolidated entities	2,814	4,471	15
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	1,986,237	1,476,588
Total assets	2,021,071	1,509,708
Amount due to UDR	(444)	2,275
Third party debt	1,147,109	877,799
Total liabilities	1,164,238	894,582
Total equity	856,833	615,126
Investment in and advances to unconsolidated joint ventures, net	431,277	327,926
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	0	0
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	0	0
Property operating expenses	52,150	33,809	25,737
Operating income/(loss)	58,393	45,995	29,096
Interest expense	(48,493)	(37,055)	(29,170)
Other income/(expense)	0	1	(9)
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	0	0	0
Cash and cash equivalents	15,245	16,454
Other assets	19,589	16,666
Accounts payable and accrued liabilities	17,573	14,508
Unconsolidated Joint Venture Vitruvian Park [Member]
Financial information relating to unconsolidated joint ventures operations
Revenues	19,376	7,680	0
Real estate depreciation and amortization	7,380	3,830	0
Net loss	(2,846)	(2,669)	0
UDR recorded loss from unconsolidated entities	(4,068)	(2,851)	0
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	278,600	283,878
Total assets	289,103	288,954
Amount due to UDR	1,960	1,352
Third party debt	123,649	120,999
Total liabilities	132,375	129,503
Total equity	156,728	159,451
Investment in and advances to unconsolidated joint ventures, net	80,302	79,318
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	0	0
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	0	0
Property operating expenses	10,711	4,633	0
Operating income/(loss)	1,285	(783)	0
Interest expense	(4,131)	(1,886)	0
Other income/(expense)	0	0	0
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	0	0	0
Cash and cash equivalents	6,570	3,498
Other assets	3,933	1,578
Accounts payable and accrued liabilities	6,766	7,152
Texas JV
Financial information relating to unconsolidated joint ventures operations
Revenues	0	0	0
Real estate depreciation and amortization	0	0	0
Net loss	(4,229)	(9,584)	(1,040)
UDR recorded loss from unconsolidated entities	(772)	(1,218)	(2,399)
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	0	0
Total assets	214,218	231,981
Amount due to UDR	0	0
Third party debt	0	0
Total liabilities	224,596	230,393
Total equity	(10,378)	1,588
Investment in and advances to unconsolidated joint ventures, net	(25,901)	(23,591)
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	224,596	230,393
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	214,218	231,981
Property operating expenses	0	0	0
Operating income/(loss)	0	0	0
Interest expense	0	0	0
Other income/(expense)	0	0	0
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	(4,229)	(9,584)	(1,040)
Cash and cash equivalents	0	0
Other assets	0	0
Accounts payable and accrued liabilities	0	0
KFH
Financial information relating to unconsolidated joint ventures operations
Revenues	19,724	19,221	18,670
Real estate depreciation and amortization	14,426	14,199	16,546
Net loss	(8,073)	(7,885)	(10,597)
UDR recorded loss from unconsolidated entities	(2,601)	(2,366)	(3,221)
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	235,623	249,097
Total assets	239,258	252,860
Amount due to UDR	531	420
Third party debt	165,209	165,209
Total liabilities	167,136	166,863
Total equity	72,122	85,997
Investment in and advances to unconsolidated joint ventures, net	21,596	25,919
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	0	0
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	0	0
Property operating expenses	7,498	7,035	6,831
Operating income/(loss)	(2,200)	(2,013)	(4,707)
Interest expense	(5,873)	(5,872)	(5,890)
Other income/(expense)	0	0	0
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	0	0	0
Cash and cash equivalents	2,507	2,289
Other assets	1,128	1,474
Accounts payable and accrued liabilities	1,396	1,234
Unconsolidated Other Joint Ventures [Domain]
Financial information relating to unconsolidated joint ventures operations
Revenues	1,579	5,324	2,724
Real estate depreciation and amortization	3,959	3,564	1,897
Net loss	(3,596)	(2,445)	(1,102)
UDR recorded loss from unconsolidated entities	576	6,224	(1,224)
Combined summary of balance sheets relating to unconsolidated joint ventures
Real estate, net	351,861	65,133
Total assets	362,303	65,216
Amount due to UDR	843	1,136
Third party debt	68,510	0
Total liabilities	87,204	3,949
Total equity	275,099	61,267
Investment in and advances to unconsolidated joint ventures, net	197,646	50,586
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	0	0
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	0	0
Property operating expenses	1,122	3,292	1,368
Operating income/(loss)	(3,502)	(1,532)	(541)
Interest expense	(94)	(913)	(561)
Other income/(expense)	0	0	0
Equity Method Investment, Summarized Financial Information, Gain (Loss) on Sale of Real Estate	0
Income/(loss) from discontinued operations	0	0	0
Cash and cash equivalents	6,239	0
Other assets	4,203	83
Accounts payable and accrued liabilities	17,851	2,813
Unconsolidated Joint Ventures [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	$ 655,519	$ 493,382