Debt instrument weighted average years to maturity.

No definition available.

Name:	udr_DebtInstrumentWeightedAverageYearsToMaturity
Namespace Prefix:	udr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Communities Encumbered.

+ References

No definition available.

+ Details

Name:	udr_NumberOfCommunitiesEncumbered
Namespace Prefix:	udr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Secured debt including debt on real estate held for sale.

+ References

No definition available.

+ Details

Name:	udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The average effective interest rate during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

Name:	us-gaap_DebtInstrumentInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

-Article 5

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

+ Details

Name:	us-gaap_UnsecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Secured and Unsecured Debt (Details) $ in Thousands	3 Months Ended	6 Months Ended
Secured and Unsecured Debt (Details) $ in Thousands	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Secured debt instruments
Weighted average interest rate	3.58%
Long-term Debt	$ 3,564,403	$ 3,564,403	$ 3,583,105
Unsecured Debt	2,213,964	$ 2,213,964	2,221,576
Weighted Average Years to Maturity		4 years 29 days
Line of Credit Facility, Amount Outstanding	2,300	$ 2,300	1,900
Fixed Rate Debt [Member]
Secured debt instruments
Principal outstanding	$ 975,024	$ 975,024	969,296
Weighted average interest rate	5.28%
Weighted Average Years to Maturity		2 years 6 months 10 days
Number of Communities Encumbered	28
Variable Rate Debt [Member]
Secured debt instruments
Principal outstanding	$ 375,415	$ 375,415	392,233
Weighted average interest rate	1.45%
Weighted Average Years to Maturity		5 years 3 months
Number of Communities Encumbered	10
Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Weighted average interest rate	5.50%
Weighted Average Years to Maturity		1 year 20 days
Number of Communities Encumbered	7
Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Weighted average interest rate	1.94%
Weighted Average Years to Maturity		1 year 6 months 25 days
Number of Communities Encumbered	1
Tax-exempt secured notes payable [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Weighted average interest rate	0.84%
Weighted Average Years to Maturity		7 years 8 months 8 days
Number of Communities Encumbered	2
Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Debt, Weighted Average Interest Rate	5.12%	5.12%
Weighted Average Years to Maturity		3 years 6 months 14 days
Number of Communities Encumbered	21
Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Debt Instrument, Interest Rate at Period End	1.63%	1.63%
Weighted Average Years to Maturity		4 years 9 months 10 days
Number of Communities Encumbered	7
Secured Debt [Member]
Secured debt instruments
Principal outstanding	$ 1,350,439	$ 1,350,439	1,361,529
Weighted average interest rate	4.22%
Long-term Debt	$ 1,350,439	$ 1,350,439
Weighted Average Years to Maturity		3 years 3 months 18 days
Number of Communities Encumbered	38
Secured Debt [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Long-term Debt	$ 975,024	$ 975,024
Secured Debt [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Long-term Debt	$ 375,415	$ 375,415
Unsecured Revolving Credit Facility due October 2015 [Member]
Secured debt instruments
Weighted average interest rate	1.12%
Weighted Average Years to Maturity		2 years 5 months 4 days
Line of Credit Facility, Amount Outstanding	$ 457,000	$ 457,000	152,500
ThreePointSevenTermNotesDueOctober2020 [Member]
Secured debt instruments
Weighted average interest rate		3.70%
Senior Notes	$ 299,958	$ 299,958	299,954
Weighted Average Years to Maturity		5 years 3 months
Four Point Six Three Percent Term Medium Notes Due January Two Thousand Twenty-Two [Member]
Secured debt instruments
Weighted average interest rate	4.63%
Senior Notes	$ 397,656	$ 397,656	397,477
Weighted Average Years to Maturity		6 years 6 months 10 days
3.75 MTN Due July 2024 [Member]
Secured debt instruments
Weighted average interest rate	3.75%
Senior Notes	$ 299,062	$ 299,062	299,010
Weighted Average Years to Maturity		9 years
1.67% Term Notes due December 2016 [Member]
Secured debt instruments
Weighted average interest rate		1.33%
Senior Notes	35,000	$ 35,000	35,000
Weighted Average Years to Maturity		2 years 11 months 1 day
2.68% Term Notes due December 2016 [Member]
Secured debt instruments
Weighted average interest rate		1.53%
Senior Notes	100,000	$ 100,000	100,000
Weighted Average Years to Maturity		2 years 11 months 4 days
Five Point Two Five Percent, Medium Term Notes, Due January 2015 [Member]
Secured debt instruments
Weighted average interest rate		0.00%
Senior Notes	0	$ 0	325,169
Weighted Average Years to Maturity
Five Point Two Five Percent, Medium Term Notes, Due January 2016 [Member]
Secured debt instruments
Weighted average interest rate		5.25%
Senior Notes	83,260	$ 83,260	83,260
Weighted Average Years to Maturity		6 months 14 days
6.21 Medium Term Note, Due January 2016 [Member]
Secured debt instruments
Weighted average interest rate		6.21%
Senior Notes	12,609	$ 12,609	0
Weighted Average Years to Maturity		1 year 3 days
2.90% Term Notes due January 2016 [Member]
Secured debt instruments
Weighted average interest rate		1.70%
Senior Notes	$ 215,000	$ 215,000	215,000
Weighted Average Years to Maturity		2 years 11 months 4 days
Eight Point Five Zero Percent, Debentures, Due September 2024 [Member]
Secured debt instruments
Weighted average interest rate	8.50%
Senior Notes	$ 15,644	$ 15,644	15,644
Weighted Average Years to Maturity		9 years 2 months 15 days
Four Point Two Five Percentage Medium-Term Notes due June 2018 [Member]
Secured debt instruments
Weighted average interest rate		4.25%
Senior Notes	298,749	$ 298,749	298,535
Weighted Average Years to Maturity		2 years 11 months 1 day
Other [Member]
Secured debt instruments
Senior Notes	$ 26	$ 26	27
Unsecured Debt [Member]
Secured debt instruments
Weighted average interest rate	3.20%
Long-term Debt	$ 2,213,964	2,213,964
Unsecured Debt	2,213,964	$ 2,213,964	2,221,576
Weighted Average Years to Maturity		4 years 6 months 21 days
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Principal outstanding	408,736	$ 408,736	401,210
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Principal outstanding	31,337	31,337	31,337
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fannie Mae credit facilities [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Principal outstanding	566,288	566,288	568,086
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fannie Mae credit facilities [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Principal outstanding	$ 249,378	$ 249,378	$ 266,196