Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013 instruments
Designated as Hedging Instrument [Member] | Interest rate swaps [Member]
Derivative [Line Items]
Number of derivative instruments (in instruments)	11
Outstanding interest rate derivatives designated as hedging instruments
Notional amount of derivative instruments designated as hedging instruments	$ 419,787
Designated as Hedging Instrument [Member] | Interest rate caps [Member]
Derivative [Line Items]
Number of derivative instruments (in instruments)	5
Outstanding interest rate derivatives designated as hedging instruments
Notional amount of derivative instruments designated as hedging instruments	274,291
Not Designated as Hedging Instrument [Member] | Interest rate caps [Member]
Derivative [Line Items]
Number of derivative instruments (in instruments)	2
Outstanding interest rate derivatives not designated as hedging instrument
Notional amount of derivative instruments not designated as hedging instruments	155,197
United Dominion Reality L.P. [Member] | Designated as Hedging Instrument [Member] | Interest rate swaps [Member]
Derivative [Line Items]
Number of derivative instruments (in instruments)	2
Outstanding interest rate derivatives designated as hedging instruments
Notional amount of derivative instruments designated as hedging instruments	96,985
United Dominion Reality L.P. [Member] | Designated as Hedging Instrument [Member] | Interest rate caps [Member]
Derivative [Line Items]
Number of derivative instruments (in instruments)	5
Outstanding interest rate derivatives designated as hedging instruments
Notional amount of derivative instruments designated as hedging instruments	255,587
United Dominion Reality L.P. [Member] | Not Designated as Hedging Instrument [Member] | Interest rate caps [Member]
Derivative [Line Items]
Number of derivative instruments (in instruments)	1
Outstanding interest rate derivatives not designated as hedging instrument
Notional amount of derivative instruments not designated as hedging instruments	$ 83,299