2.4.0.82409402 - Disclosure - Joint Ventures (Details)truefalseIn Thousands, unless otherwise specifiedfalse1false 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$1true 4us-gaap_EquityMethodInvestmentSummarizedFinancialInformationIncomeStatementAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financial information relating to unconsolidated joint ventures operations2false 5us-gaap_IncomeLossFromEquityMethodInvestmentsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse515000515USD$falsetruefalse2truefalsefalse-2412000-2412USD$falsetruefalse3truefalsefalse-2287000-2287USD$falsetruefalse4truefalsefalse-5103000-5103USD$falsetruefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -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. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 19 -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 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.12) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 11 -Article 7 false2UDR recorded loss from unconsolidated entities3true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures4false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse558804000558804USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse558804000558804USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse507037000507037USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures5false 5us-gaap_DeferredGainOnSaleOfPropertyus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-25469000-25469USD$falsefalsefalse2truefalsefalse-29406000-29406USD$falsefalsefalse3truefalsefalse-25469000-25469USD$falsefalsefalse4truefalsefalse-29406000-29406USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 40 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.U.Q2) -URI http://asc.fasb.org/extlink&oid=6955272&loc=d3e221323-122791 false2Deferred fees and gains on the sale of depreciable property6false 5udr_InvestmentInAndAdvancesToUnconsolidatedJointVenturesNetudr_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse533335000533335USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse533335000533335USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse477631000477631USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestment In and Advances to Unconsolidated Joint Ventures, NetNo definition available.false2Investment in and advances to unconsolidated joint ventures, net7false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse6false USDtruefalse$D2013Q2_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVenturesMemberhttp://www.sec.gov/CIK0000074208duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseUnconsolidated Joint Ventures [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVenturesMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Unconsolidated Joint Ventures [Member]8true 4us-gaap_EquityMethodInvestmentSummarizedFinancialInformationIncomeStatementAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financial information relating to unconsolidated joint ventures operations9false 5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenueus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse6260700062607USD$falsefalsefalse2truefalsefalse7472500074725USD$falsefalsefalse3truefalsefalse123687000123687USD$falsefalsefalse4truefalsefalse137750000137750USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.No definition available.false2Revenues10false 5udr_EquityMethodInvestmentSummarizedFinancialInformationDepreciationAmortizationudr_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2133600021336USD$falsefalsefalse2truefalsefalse2648900026489USD$falsefalsefalse3truefalsefalse4311400043114USD$falsefalsefalse4truefalsefalse5237400052374USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of depreciation and amortization reported by an equity method investment of the entity.No definition available.false2Real estate depreciation and amortization11false 5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2364200023642USD$falsefalsefalse2truefalsefalse35440003544USD$falsefalsefalse3truefalsefalse2747900027479USD$falsefalsefalse4truefalsefalse-5077000-5077USD$falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of net income (loss) reported by an equity method investment of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(g)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph g -Subparagraph 1, 2 -Article 4 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph w -Article 1 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph d -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 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph bb -Article 1 false2Equity Method Investment, Summarized Financial Information, Net Income (Loss)12true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures13false 5udr_EquityMethodInvestmentSummarizedFinancialInformationRealEstateNetudr_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse32352280003235228USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse32352280003235228USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse31898140003189814USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of net real estate assets reported by an equity method investment of the entity.No definition available.false2Real estate, net14false 5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssetsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse33031950003303195USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse33031950003303195USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse32665180003266518USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of assets reported by an equity method investment of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(g)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph g -Subparagraph 1, 2 -Article 4 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph w -Article 1 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph d -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 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph bb -Article 1 false2Total assets15false 5udr_EquityMethodInvestmentSummarizedFinancialInformationAmountDueToRelatedPartyudr_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse3273100032731USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse3273100032731USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse3484300034843USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount due to UDR by an equity method investment of the entity.No definition available.false2Amount due to UDR16false 5udr_EquityMethodInvestmentSummarizedFinancialInformationAmountOfDebtDueToThirdPartiesudr_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse17732830001773283USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse17732830001773283USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse16634270001663427USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of debt due to third parties by an equity method investment of the entity.No definition available.false2Third party debt17false 5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilitiesus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse18469610001846961USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse18469610001846961USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse17478550001747855USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of liabilities reported by an equity method investment of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(g)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph g -Subparagraph 1, 2 -Article 4 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph w -Article 1 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph d -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 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph bb -Article 1 false2Total liabilities18false 5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationEquityus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse14562340001456234USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse14562340001456234USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse15186630001518663USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of equity, including noncontrolling interest, reported by an equity method investment of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph d -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Total equity19false 5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationMinorityInterestus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse00USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse1275500012755USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of equity attributable to noncontrolling interests of an equity method investment of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(g)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph g -Subparagraph 1, 2 -Article 4 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph w -Article 1 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph d -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 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 9: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph bb -Article 1 false2Equity held by non-controlling interest20false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse11false truefalseI2013Q2_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureVitruvianParkMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseUnconsolidated Joint Venture Vitruvian Park [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureVitruvianParkMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMembernumberStandardhttp://www.xbrl.org/2003/instancepurexbrli0nanafalse0Unconsolidated Joint Venture Vitruvian Park [Member]21true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures22false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.5000.500falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.5000.500falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment23false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse12false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_OperatingCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureOneUDRMetLifePartnershipMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseOperating Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_OperatingCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture UDR Met Life I Partnership [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureOneUDRMetLifePartnershipMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberCommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0Apartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Operating Community [Member] | Unconsolidated Joint Venture UDR Met Life I Partnership [Member]24true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures25false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5245500052455USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse5245500052455USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse7512900075129USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures26false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.1320.132falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.1320.132falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment27false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse16411641falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse16411641falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes28false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse88falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse88falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned29false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse14false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_OperatingCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureSevenUdrMetlifeIiPartnershipMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseOperating Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_OperatingCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture UDR MetLife II Partnership [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureSevenUdrMetlifeIiPartnershipMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberApartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0CommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Operating Community [Member] | Unconsolidated Joint Venture UDR MetLife II Partnership [Member]30true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures31false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse323401000323401USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse323401000323401USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse327001000327001USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures32false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.5000.500falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.5000.500falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment33false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse31193119falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse31193119falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes34false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1515falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse1515falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned35false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse16false truefalseI2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_OperatingCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureVitruvianParkMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseOperating Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_OperatingCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Vitruvian Park [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureVitruvianParkMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberApartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0nanafalse0Operating Community [Member] | Unconsolidated Joint Venture Vitruvian Park [Member]36true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures37false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse8016200080162falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse8016200080162falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures38false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.5000.500falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.5000.500falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment39false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse739739falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse739739falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes40false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse22falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse22falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned41false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse19false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_OperatingCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseOperating Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_OperatingCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Two Stoughton Massachusetts [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberApartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0CommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Operating Community [Member] | Unconsolidated Joint Venture Two Stoughton Massachusetts [Member]42true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures43false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1602000016020USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse1602000016020USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse1631100016311USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures44false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.9500.950falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.9500.950falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment45false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse240240falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse240240falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes46false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse11falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse11falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned47false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse21false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_OperatingCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureThreeMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseOperating Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_OperatingCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Three [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureThreeMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberCommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0Apartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Operating Community [Member] | Unconsolidated Joint Venture Three [Member]48true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures49false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2773900027739USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse2773900027739USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse2966300029663USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures50false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.3000.300falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.3000.300falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment51false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse660660falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse660660falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes52false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse33falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse33falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned53false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse23false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_OperatingCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureFourTexasMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseOperating Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_OperatingCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Four Texas [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureFourTexasMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberApartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0CommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Operating Community [Member] | Unconsolidated Joint Venture Four Texas [Member]54true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures55false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse19990001999USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse19990001999USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse34570003457USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures56false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.2000.200falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.2000.200falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment57false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse33593359falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse33593359falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes58false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse88falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse88falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned59false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse25false truefalseI2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_DevelopmentCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureVitruvianParkMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseDevelopment Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_DevelopmentCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Vitruvian Park [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureVitruvianParkMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMembernumberStandardhttp://www.xbrl.org/2003/instancepurexbrli0nanafalse0Development Community [Member] | Unconsolidated Joint Venture Vitruvian Park [Member]60true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures61false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse391391falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse391391falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes62false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse11falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse11falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned63false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse27false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_DevelopmentCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureFiveSanDiegoCaliforniaMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseDevelopment Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_DevelopmentCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Five San Diego California [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureFiveSanDiegoCaliforniaMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberApartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0CommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Development Community [Member] | Unconsolidated Joint Venture Five San Diego California [Member]64true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures65false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse3092000030920USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse3092000030920USD$falsefalsefalse4falsefalsefalse00falsefalsefalse5truefalsefalse2993000029930USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures66false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.9500.950falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.9500.950falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment67false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse264264falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse264264falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes68false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse11falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse11falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned69false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse29false USDtruefalse$I2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_udr_DevelopmentCommunityMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureSixCollegeParkCaliforniaMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseDevelopment Community [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldiudr_DevelopmentCommunityMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Six College Park California [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureSixCollegeParkCaliforniaMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberApartment_HomesStandardhttp://www.udr.com/20130630Apartment_Homesudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0CommunitiesStandardhttp://www.udr.com/20130630Communitiesudr0usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Development Community [Member] | Unconsolidated Joint Venture Six College Park California [Member]70true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures71false 5us-gaap_EquityMethodInvestmentsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2610800026108USD$falsetruefalse2falsefalsefalse00falsefalsefalse3truefalsefalse2610800026108USD$falsetruefalse4falsefalsefalse00falsefalsefalse5truefalsefalse2554600025546USD$falsetruefalsexbrli:monetaryItemTypemonetaryThis item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.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 210.5-02.12) -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 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570 false2Investment in unconsolidated joint ventures72false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.9500.950falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.9500.950falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment73false 5us-gaap_NumberOfUnitsInRealEstatePropertyus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse256256falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse256256falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of units in a real estate property owned as of the balance sheet date.No definition available.false256Number of apartment homes74false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse11falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse11falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned75false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse31false truefalseI2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_us-gaap_LandMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureOneUDRMetLifePartnershipMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseLand [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_LandMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture UDR Met Life I Partnership [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureOneUDRMetLifePartnershipMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberLand_ParcelsStandardhttp://www.udr.com/20130630Land_Parcelsudr0numberStandardhttp://www.xbrl.org/2003/instancepurexbrli0nanafalse0Land [Member] | Unconsolidated Joint Venture UDR Met Life I Partnership [Member]76true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures77false 5us-gaap_EquityMethodInvestmentOwnershipPercentageus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.0430.043falsefalsefalse2falsefalsefalse00falsefalsefalse3truetruefalse0.0430.043falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -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 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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. false0Ownership percentage, equity method investment78false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse88falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse88falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities Owned79false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalse32false truefalseI2013Q2_us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_us-gaap_LandMember_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_udr_UnconsolidatedJointVentureVitruvianParkMemberhttp://www.sec.gov/CIK0000074208instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseLand [Member]us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_LandMemberus-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxisexplicitMemberfalsefalseUnconsolidated Joint Venture Vitruvian Park [Member]us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisxbrldihttp://xbrl.org/2006/xbrldiudr_UnconsolidatedJointVentureVitruvianParkMemberus-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxisexplicitMemberLand_ParcelsStandardhttp://www.udr.com/20130630Land_Parcelsudr0nanafalse0Land [Member] | Unconsolidated Joint Venture Vitruvian Park [Member]80true 4udr_EquityMethodInvestmentSummarizedFinancialInformationBalanceSheetsAbstractudr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Combined summary of balance sheets relating to unconsolidated joint ventures81false 5us-gaap_NumberOfRealEstatePropertiesus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse66falsefalsefalse2falsefalsefalse00falsefalsefalse3truefalsefalse66falsefalsefalse4falsefalsefalse00falsefalsefalse5falsefalsefalse00falsefalsefalsexbrli:integerItemTypeintegerThe number of real estate properties owned as of the balance sheet date.No definition available.false256Joint Venture and Partnership Number of Operating Communities OwnedfalseJoint Ventures (Details) (USD $)ThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.udr.com/role/JointVenturesDetails581