2.4.0.82421406 - Disclosure - Derivatives and Hedging Activity (Details Textual)truefalsefalse1false USDfalsefalse$D2013Q2http://www.sec.gov/CIK0000074208duration2013-04-01T00:00:002013-06-30T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$D2012Q2http://www.sec.gov/CIK0000074208duration2012-04-01T00:00:002012-06-30T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$3false USDfalsefalse$D2013Q2YTDhttp://www.sec.gov/CIK0000074208duration2013-01-01T00:00:002013-06-30T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$4false USDfalsefalse$D2012Q2YTDhttp://www.sec.gov/CIK0000074208duration2012-01-01T00:00:002012-06-30T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$5false USDfalsefalse$I2012Q4http://www.sec.gov/CIK0000074208instant2012-12-31T00:00:000001-01-01T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 3us-gaap_DerivativesFairValueLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Derivatives, Fair Value [Line Items]2false 4us-gaap_DerivativeCollateralObligationToReturnCashus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse00USD$falsetruefalse2falsefalsefalse00falsefalsefalse3truefalsefalse00USD$falsetruefalse4falsefalsefalse00falsefalsefalse5truefalsefalse00USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe amount of the obligation to return cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41678-113959 false2Derivative, Collateral, Obligation to Return Cash3true 2udr_DerivativesAndHedgingActivityTextualAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Derivatives And Hedging Activity (Textual) [Abstract]4false 3us-gaap_IneffectivenessOnInterestRateFairValueHedgesIsImmaterialus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00less than a  $1,000falsefalsefalse2falsefalsefalse00less than a  $1,000falsefalsefalse3falsefalsefalse00less than a  $1,000falsefalsefalse4falsefalsefalse00less than a  $1,000falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringAssertion that the amount of fair value hedge ineffectiveness is immaterial.No definition available.false0Cash flow hedge ineffectiveness in earnings materiality5false 3us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNetus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse56000005600000falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse56000005600000falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80748-113994 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph b(2) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Estimated additional accumulated other comprehensive Income/(Loss) transferred to interest expense6false 3us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-3000-3000falsefalsefalse2truefalsefalse-7000-7000falsefalsefalse3truefalsefalse-5000-5000falsefalsefalse4truefalsefalse291000291000falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryNet gain (loss) from the increase (decrease) in fair value of derivative instrument not designated as hedging instrument.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph b(1)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Derivative instruments not designated as hedging instruments, gain (loss), net7false 3us-gaap_DerivativeNetLiabilityPositionAggregateFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse80000008000000falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse80000008000000falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Fair value of derivatives in a net liability position8false 3us-gaap_AssetsNeededForImmediateSettlementAggregateFairValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse80000008000000USD$falsetruefalse2falsefalsefalse00falsefalsefalse3truefalsefalse80000008000000USD$falsetruefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate fair value of assets needed to immediately settle the derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959 false2Payment required to pay for contract terminationfalseDerivatives and Hedging Activity (Details Textual) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.udr.com/role/DerivativesAndHedgingActivityDetailsTextual58