Debt (UNITED DOMINION REALTY, L.P.) (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) Communities	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Weighted average interest rate	3.58%
Debt Instrument Weighted Average Years to Maturity		4 years 29 days
Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	$ 975,024	$ 975,024	$ 969,296
Weighted average interest rate	5.28%
Debt Instrument Weighted Average Years to Maturity		2 years 6 months 10 days
Number of Communities Encumbered (in communities)	28
Fixed Rate Debt [Member] \| Mortgages Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate	5.50%
Debt Instrument Weighted Average Years to Maturity		1 year 20 days
Number of Communities Encumbered (in communities)	7
Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity		3 years 6 months 14 days
Number of Communities Encumbered (in communities)	21
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	$ 375,415	$ 375,415	392,233
Weighted average interest rate	1.45%
Debt Instrument Weighted Average Years to Maturity		5 years 3 months
Number of Communities Encumbered (in communities)	10
Variable Rate Debt [Member] \| Mortgages Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.94%
Debt Instrument Weighted Average Years to Maturity		1 year 6 months 25 days
Number of Communities Encumbered (in communities)	1
Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity		4 years 9 months 10 days
Number of Communities Encumbered (in communities)	7
Variable Rate Debt [Member] \| Tax Exempt Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate	0.84%
Debt Instrument Weighted Average Years to Maturity		7 years 8 months 8 days
Number of Communities Encumbered (in communities)	2
United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Principal outstanding	$ 912,567	$ 912,567	931,959
Weighted average interest rate		4.43%
Debt Instrument Weighted Average Years to Maturity		3 years 6 months 14 days
Number of Communities Encumbered (in communities) \| Communities		20
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	708,058	$ 708,058	712,199
Weighted average interest rate		5.21%
Debt Instrument Weighted Average Years to Maturity		2 years 6 months
Number of Communities Encumbered (in communities) \| Communities		14
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member] \| Mortgages Notes Payable [Member]
Debt Instrument [Line Items]
Principal outstanding	374,056	$ 374,056	378,371
Weighted average interest rate		5.49%
Debt Instrument Weighted Average Years to Maturity		1 year 1 month 6 days
Number of Communities Encumbered (in communities) \| Communities		5
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Weighted average interest rate		4.90%
Debt Instrument Weighted Average Years to Maturity		4 years 25 days
Number of Communities Encumbered (in communities) \| Communities		9
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	204,509	$ 204,509	219,760
Weighted average interest rate		1.74%
Debt Instrument Weighted Average Years to Maturity		7 years 1 month 17 days
Number of Communities Encumbered (in communities) \| Communities		6
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Weighted average interest rate		1.88%
Debt Instrument Weighted Average Years to Maturity		5 years 8 months 1 day
Number of Communities Encumbered (in communities) \| Communities		5
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member] \| Tax Exempt Notes Payable [Member]
Debt Instrument [Line Items]
Principal outstanding	27,000	$ 27,000	27,000
Weighted average interest rate		0.85%
Debt Instrument Weighted Average Years to Maturity		16 years 8 months 19 days
Number of Communities Encumbered (in communities) \| Communities		1
Fannie Mae credit facilities [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	566,288	$ 566,288	568,086
Fannie Mae credit facilities [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	249,378	249,378	266,196
Fannie Mae credit facilities [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	334,002	334,002	333,828
Fannie Mae credit facilities [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	$ 177,509	$ 177,509	$ 192,760