Unaudited Summarized Consolidated Quarterly Financial Data (UNITED DOMINION REALTY, L.P.) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended			9 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	Sep. 30, 2013
Quarterly Financial Data [Abstract]
Rental income	$ 206,104	[1]	$ 203,587	[1]	$ 200,959	[1]	$ 194,352	[1]	$ 190,321	[1]	$ 187,917	[1]	$ 186,285	[1]	$ 181,961	[1]
Income/(loss) from continuing operations	6,485		10,611		4,359		(5,195)		(3,374)		2,351		4,525		(1,162)		16,260	2,340	(46,305)
Income/(loss) from discontinued operations	0		79		18		(87)		41,376		884		829		853		10	43,942	266,608
Net income																	154,334	44,812	212,177
Net (loss)/income attributable to stakeholders	64,486		39,618		29,076		17,430		35,769		2,257		4,261		(1,199)		150,610	41,088	203,376
Earnings per weighted average common share - basic and diluted:
Net (loss)/income attributable to common stockholders — basic and diluted (in dollars per share)	$ 0.25	[2]	$ 0.16	[2]	$ 0.12	[2]	$ 0.07	[2]	$ 0.14	[2]	$ 0.01	[2]	$ 0.02	[2]	$ 0.00	[2]
United Dominion Reality L.P.
Quarterly Financial Data [Abstract]
Rental income	107,978	[1]	107,444	[1]	104,842	[1]	102,370	[1]	102,104	[1]			100,421	[1]	97,770	[1]	422,634	401,853	384,946	101,558	[1]
Income/(loss) from continuing operations	9,939		8,875		8,319		6,411		6,488				9,339		6,870		33,544	32,766	(13,309)	10,069
Income/(loss) from discontinued operations									42,407				882		905		0	45,176	57,643	982
Net income	$ 32,631		$ 8,637		$ 24,426		$ 30,533		$ 44,482				$ 10,154		$ 7,729		$ 96,227	$ 73,376	$ 43,982	$ 11,011
Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted	$ 0.18	[3]	$ 0.05	[3]	$ 0.13	[3]	$ 0.17	[3]	$ 0.24				$ 0.06		$ 0.04		$ 0.53	$ 0.40	$ 0.24	$ 0.06

[1] Represents rental income from continuing operations, excluding amounts classified as discontinued operations.

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

[3] Quarterly income/(loss) per OP Unit amounts may not total to the annual amounts