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Line of Credit Facility, Commitment Fee Description Range High

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Line of Credit Facility, Commitment Fee Description Range Low

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Line of Credit Facility, Description Range High

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Line of Credit Facility, Description Range Low

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Number of extension options on loan

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Percentage of Debt Instrument Price

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Portion of Medium Term Note subject to Interest Rate Swaps

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Secured Debt, Encumbers Real Estate Owned, Percent.

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Secured debt including debt on real estate held for sale.

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Secured debt.

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Secured Debt, Unencumbered Real Estate Owned, Percent.

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The average effective interest rate during the reporting period.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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When presenting a range of interest rates, the highest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

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When presenting a range of interest rates, the lowest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average interest rate of debt outstanding.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Description of the fees for amounts available, but unused under the credit facility.

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The effective interest rate at the end of the reporting period.

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Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Weighted average interest rate of long-term debt outstanding.

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Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Secured Debt and Unsecured Debt (Details Textual)			1 Months Ended	9 Months Ended	12 Months Ended
Secured Debt and Unsecured Debt (Details Textual)	Jun. 27, 2014	Sep. 26, 2013	Oct. 20, 2015	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Debt Instrument [Line Items]
Amortization of Financing Costs					$ 7,000,000	$ 7,200,000
Secured Debt (Textual) [Abstract]
Secured debt amount which encumbers real estate owned based upon book value					$ 2,400,000,000
Percentage of secured debt which encumbers real estate owned based upon book value					25.90%
Secured debt amount of real estate owned which is unencumbered					$ 6,800,000,000
Percentage of secured debt of real estate owned which is unencumbered					74.10%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt					$ 96,486,000
Unamortized fair market adjustment					$ 10,000,000	6,700,000
Weighted Average Interest Rate					3.74%
Long-term Line of Credit					$ 2,300,000	1,900,000
Number of extension options on loan			2
Extension period of option on loan			6 months
Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 952,801,000	963,713,000
Weighted Average Interest Rate					4.93%
Variable Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 424,144,000	390,608,000
Weighted Average Interest Rate					1.53%
Five Point Two Five Percent, Medium Term Notes, Due January 2015 [Member]
Secured Debt (Textual) [Abstract]
Unamortized fair market adjustment					$ 0	6,000
Weighted Average Interest Rate					0.00%
Senior Notes					$ 0	325,169,000
3.75 MTN Due July 2024 [Member]
Secured Debt (Textual) [Abstract]
Unamortized fair market adjustment					$ 938,000	990,000
Weighted Average Interest Rate					3.75%
Debt Instrument, Maturity Date	Jul. 31, 2024
Senior Notes					$ 299,114,000	299,010,000
Mortgages [Member] \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Debt instrument, maturity date range, start					Jun. 01, 2016
Debt instrument, maturity date range, end					Nov. 01, 2025
Notes payable minimum interest rates range					3.43%
Notes payable maximum interest rates range					6.16%
Weighted Average Interest Rate					4.57%
Mortgages [Member] \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					2.19%
Debt Assumed As Part of Acquisition [Member]
Secured Debt (Textual) [Abstract]
Amortization of Debt Discount (Premium)					$ 5,300,000	5,100,000	$ 5,100,000
Fannie Mae credit facilities \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Debt instrument, maturity date range, start					May 01, 2017
Debt instrument, maturity date range, end					Jul. 01, 2023
Debt, Weighted Average Interest Rate					5.23%
Fannie Mae credit facilities \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Interest rate at the end of the period					1.71%
Tax-exempt secured notes payable \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Debt instrument, maturity date range, start					Aug. 01, 2019
Debt instrument, maturity date range, end					Mar. 20, 2032
Notes payable minimum interest rates range					0.75%
Notes payable maximum interest rates range					0.76%
Unsecured Revolving Credit Facility due October 2015
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					1.19%
Long-term Line of Credit					$ 150,000,000	152,500,000
4.63% Medium-Term Notes due January 2022
Secured Debt (Textual) [Abstract]
Unamortized fair market adjustment					$ 2,164,000	2,523,000
Weighted Average Interest Rate					4.63%
Senior Notes					$ 397,836,000	397,477,000
ThreePointSevenTermNotesDueOctober2020 [Member]
Secured Debt (Textual) [Abstract]
Debt Instrument, Maturity Date		Oct. 01, 2020
Senior Notes					299,962,000	299,954,000
Fannie Mae
Secured Debt (Textual) [Abstract]
Long-term Line of Credit					$ 813,840,000	$ 834,282,000
Interest rate at the end of the period					3.93%	4.00%
Unsecured Debt [Member]
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					3.64%
Line of Credit Facility, Interest Rate Description					95
Line of Credit Facility, Description Range Low					90
Line of Credit Facility, Description Range High					175
Unsecured Working Capital Credit Facility due January 2019 [Member]
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					0.00%
Long-term Line of Credit					$ 0	$ 0
Line of Credit Facility, Interest Rate Description					90
Line of Credit Facility, Description Range Low					85
Line of Credit Facility, Description Range High					155
Revolving Credit Facility [Member]
Secured Debt (Textual) [Abstract]
Line of Credit Facility, Interest Rate Description					90
Line of Credit Facility, Commitment Fee Description					15
Line of Credit Facility, Description Range Low					85
Line of Credit Facility, Description Range High					155
Line of Credit Facility, Commitment Fee Description Range Low					12.5
Line of Credit Facility, Commitment Fee Description Range High					30
4.00% MTN Due October 2025 [Member]
Secured Debt (Textual) [Abstract]
Unamortized fair market adjustment					$ 671,000	0
Portion of Medium Term Note subject to Interest Rate Swaps					200,000,000
Medium-term Notes					$ 300,000,000
Weighted Average Interest Rate					4.00%
Fixed interest rate					4.00%
Debt Instrument, Maturity Date				Oct. 01, 2025
Percentage of Debt Instrument Price					99.77%
Long-term Debt, Weighted Average Interest Rate					4.55%
Senior Notes					$ 299,329,000	0
Five Point Two Five Percent, Medium Term Notes, Due January 2016 [Member]
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					5.25%
Senior Notes					$ 83,260,000	83,260,000
6.21 Medium Term Note, Due January 2016 [Member]
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					6.21%
Senior Notes					$ 12,091,000	0
UDR Bank Credit Facility
Secured Debt (Textual) [Abstract]
Credit facilities with aggregate commitment					$ 2,000,000,000	$ 900,000,000
Interest rate at the end of the period					1.20%	1.10%
UDR Bank Credit Facility \| Unsecured Debt [Member]
Secured Debt (Textual) [Abstract]
Credit facilities with aggregate commitment					$ 350,000,000
UDR Bank Credit Facility \| Revolving Credit Facility [Member]
Secured Debt (Textual) [Abstract]
Credit facilities with aggregate commitment					1,100,000,000
Unsecured Working Capital Credit Facility due January 2019 [Member]
Secured Debt (Textual) [Abstract]
Credit facilities with aggregate commitment					$ 30,000,000
Beginning of range of initial term of debt [Member] \| Fannie Mae credit facilities
Secured Debt (Textual) [Abstract]
Debt Instrument, Term					7 years
End of range of inital term of debt [Member] \| Fannie Mae credit facilities
Secured Debt (Textual) [Abstract]
Debt Instrument, Term					10 years
Fair Value, Measurements, Recurring [Member] \| Fannie Mae credit facilities \| Reported Value Measurement [Member] \| Fannie Mae credit facilities \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 514,462,000	$ 568,086,000
Fair Value, Measurements, Recurring [Member] \| Fannie Mae credit facilities \| Reported Value Measurement [Member] \| Fannie Mae credit facilities \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					299,378,000	266,196,000
Fair Value, Measurements, Recurring [Member] \| Mortgages [Member] \| Reported Value Measurement [Member] \| Mortgages [Member] \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					442,617,000	401,210,000
Fair Value, Measurements, Recurring [Member] \| Mortgages [Member] \| Reported Value Measurement [Member] \| Mortgages [Member] \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					31,337,000	31,337,000
United Dominion Reality L.P.
Debt Instrument [Line Items]
Amortization of Financing Costs					1,300,000	1,400,000
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 475,964,000	927,484,000
Weighted Average Interest Rate					3.76%
United Dominion Reality L.P. \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 279,333,000	708,534,000
Weighted Average Interest Rate					4.90%
United Dominion Reality L.P. \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 196,631,000	218,950,000
Weighted Average Interest Rate					1.74%
United Dominion Reality L.P. \| Mortgages [Member] \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Notes payable minimum interest rates range					3.43%
Secured Debt Including Debt on Real Estate Held for Sale					$ 30,132,000	378,371,000
Weighted Average Interest Rate					3.43%
United Dominion Reality L.P. \| Fannie Mae credit facilities \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					5.08%
United Dominion Reality L.P. \| Fannie Mae credit facilities \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Weighted Average Interest Rate					1.90%
United Dominion Reality L.P. \| 4.63% Medium-Term Notes due January 2022
Secured Debt (Textual) [Abstract]
Debt instrument, maturity date range, end				Jan. 01, 2022
United Dominion Reality L.P. \| Fannie Mae
Secured Debt (Textual) [Abstract]
Long-term Line of Credit					$ 421,031,000	$ 526,588,000
Interest rate at the end of the period					3.80%	4.00%
United Dominion Reality L.P. \| Fair Value, Measurements, Recurring [Member] \| Fannie Mae credit facilities \| Reported Value Measurement [Member] \| Fannie Mae credit facilities \| Fixed Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					$ 250,828,000	$ 333,828,000
United Dominion Reality L.P. \| Fair Value, Measurements, Recurring [Member] \| Fannie Mae credit facilities \| Reported Value Measurement [Member] \| Fannie Mae credit facilities \| Variable Rate Debt
Secured Debt (Textual) [Abstract]
Secured Debt Including Debt on Real Estate Held for Sale					170,203,000	$ 192,760,000
Financial Guarantee \| United Dominion Reality L.P. \| 3.75 MTN Due July 2024 [Member]
Secured Debt (Textual) [Abstract]
Guarantor borrowing capacity				$ 300,000,000
Financial Guarantee \| United Dominion Reality L.P. \| 4.63% Medium-Term Notes due January 2022
Secured Debt (Textual) [Abstract]
Guarantor borrowing capacity				400,000,000
Financial Guarantee \| United Dominion Reality L.P. \| 2.90% Term Notes due January 2016
Secured Debt (Textual) [Abstract]
Guarantor borrowing capacity					250,000,000
Financial Guarantee \| United Dominion Reality L.P. \| 1.68% Term Notes due December 2016
Secured Debt (Textual) [Abstract]
Guarantor borrowing capacity					$ 100,000,000
Financial Guarantee \| United Dominion Reality L.P. \| 4.00% MTN Due October 2025 [Member]
Secured Debt (Textual) [Abstract]
Guarantor borrowing capacity				$ 300,000,000