Fair Value of Derivatives and Financial Instruments (UNITED DOMINION REALTY, L.P.) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 88		$ 0
Derivatives - Interest rate contracts	10,368		4,965
Fair Value | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	14,896		83,833
Secured debt instruments - variable rate
Total liabilities	3,721,512		3,651,141
Fair Value | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	88
Derivatives - Interest rate contracts	10,368	[1]	4,965	[2]
Fair Value | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	415,663	[2]	466,375	[3]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	31,337	[2]	63,595	[3]
Fair Value | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	94,700	[2]	94,700	[3]
Fair Value | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	606,623	[2]	661,094	[3]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	266,196	[2]	211,409	[3]
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	0		0
Secured debt instruments - variable rate
Total liabilities	0		0
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivatives - Interest rate contracts	0		0
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
Fair Value | Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	88		0
Secured debt instruments - variable rate
Total liabilities	10,368		4,965
Fair Value | Significant Other Observable Inputs (Level 2) | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	88
Derivatives - Interest rate contracts	10,368
Fair Value | Significant Other Observable Inputs (Level 2) | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
Fair Value | Significant Other Observable Inputs (Level 2) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
Fair Value | Significant Other Observable Inputs (Level 2) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
Fair Value | Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	14,808		83,833
Secured debt instruments - variable rate
Total liabilities	3,711,144		3,646,176
Fair Value | Significant Unobservable Inputs (Level 3) | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivatives - Interest rate contracts	0		0
Fair Value | Significant Unobservable Inputs (Level 3) | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	415,663		466,375
Secured debt instruments - variable rate
Secured debt instruments - variable rate	31,337		63,595
Fair Value | Significant Unobservable Inputs (Level 3) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	94,700		94,700
Fair Value | Significant Unobservable Inputs (Level 3) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	606,623		661,094
Secured debt instruments - variable rate
Secured debt instruments - variable rate	266,196		211,409
Carrying Amount | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	14,457		83,033
Secured debt instruments - variable rate
Total liabilities	3,593,473		3,528,668
Carrying Amount | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts			4,965	[2]
Carrying Amount | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate			445,706	[3]
Secured debt instruments - variable rate
Secured debt instruments - variable rate			63,595	[3]
Carrying Amount | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate			94,700	[3]
Carrying Amount | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate			626,667	[3]
Secured debt instruments - variable rate
Secured debt instruments - variable rate			211,409	[3]
United Dominion Reality L.P.
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	39		0
Derivatives - Interest rate contracts	918		2,731
United Dominion Reality L.P. | Fair Value | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	39
Secured debt instruments - variable rate
Total liabilities	967,983		969,724
United Dominion Reality L.P. | Fair Value | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	39	[4]
Derivatives - Interest rate contracts	918	[4]	2,731	[4]
United Dominion Reality L.P. | Fair Value | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	391,835	[5]	403,695	[5]
United Dominion Reality L.P. | Fair Value | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	27,000	[5]	27,000	[5]
United Dominion Reality L.P. | Fair Value | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	355,470	[5]	394,239	[5]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	192,760	[5]	142,059	[5]
United Dominion Reality L.P. | Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	0
Secured debt instruments - variable rate
Total liabilities	0		0
United Dominion Reality L.P. | Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivatives - Interest rate contracts	0		0
United Dominion Reality L.P. | Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
United Dominion Reality L.P. | Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
United Dominion Reality L.P. | Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
United Dominion Reality L.P. | Fair Value | Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	39
Secured debt instruments - variable rate
Total liabilities	918		2,731
United Dominion Reality L.P. | Fair Value | Significant Other Observable Inputs (Level 2) | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	39
Derivatives - Interest rate contracts	918		2,731
United Dominion Reality L.P. | Fair Value | Significant Other Observable Inputs (Level 2) | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
United Dominion Reality L.P. | Fair Value | Significant Other Observable Inputs (Level 2) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
United Dominion Reality L.P. | Fair Value | Significant Other Observable Inputs (Level 2) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0		0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0		0
United Dominion Reality L.P. | Fair Value | Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	0
Secured debt instruments - variable rate
Total liabilities	967,065		966,993
United Dominion Reality L.P. | Fair Value | Significant Unobservable Inputs (Level 3) | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0
Derivatives - Interest rate contracts	0		0
United Dominion Reality L.P. | Fair Value | Significant Unobservable Inputs (Level 3) | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	391,835		403,695
United Dominion Reality L.P. | Fair Value | Significant Unobservable Inputs (Level 3) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	27,000		27,000
United Dominion Reality L.P. | Fair Value | Significant Unobservable Inputs (Level 3) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	355,470		394,239
Secured debt instruments - variable rate
Secured debt instruments - variable rate	192,760		142,059
United Dominion Reality L.P. | Carrying Amount | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	39
Secured debt instruments - variable rate
Total liabilities	932,877		937,596
United Dominion Reality L.P. | Carrying Amount | Interest rate contracts | Fair Value, Measurements, Recurring
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	39	[4]
Derivatives - Interest rate contracts	918	[4]	2,731	[4]
United Dominion Reality L.P. | Carrying Amount | Mortgage notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	378,371	[5]	386,803	[5]
United Dominion Reality L.P. | Carrying Amount | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring
Secured debt instruments - variable rate
Secured debt instruments - variable rate	27,000	[5]	27,000	[5]
United Dominion Reality L.P. | Carrying Amount | Fannie Mae credit facilities | Fair Value, Measurements, Recurring
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	333,828	[5]	379,003	[5]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	$ 192,760	[5]	$ 142,059	[5]

[1] See Note 6, Secured Debt and Unsecured Debt.

[2] See Note 2, Significant Accounting Policies.

[3] See Note 13, Derivatives and Hedging Activity.

[4] See Note 8, Derivatives and Hedging Activity

[5] See Note 5, Debt