UDR (UDR) 10-Q28 Apr 152015 Q1 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
Document and Entity Information	Mar. 31, 2015	Apr. 27, 2015
Entity Registrant Name	UDR, Inc.
Entity Central Index Key	74208
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		258,985,923
United Dominion Reality L.P. [Member]
Entity Registrant Name	United Dominion Realty L.P.
Entity Central Index Key	1018254
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		0

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Real estate owned:
Real estate held for investment	$8,256,995	$8,205,627
Less: accumulated depreciation	-2,521,958	-2,434,772
Real estate held for investment, net	5,735,037	5,770,855
Real estate under development (net of accumulated depreciation of $142 and $0, respectively)	196,511	177,632
Total real estate owned, net of accumulated depreciation	5,931,548	5,948,487
Cash and cash equivalents	6,274	15,224
Restricted cash	23,266	22,340
Deferred financing costs, net	21,676	22,686
Notes receivable, net	15,494	14,369
Investment in and advances to unconsolidated joint ventures, net	763,540	718,226
Other assets	96,713	105,202
Total assets	6,858,511	6,846,534
Liabilities:
Secured debt	1,370,673	1,361,529
Unsecured debt	2,145,996	2,221,576
Real estate taxes payable	21,848	15,978
Accrued interest payable	23,460	34,215
Security deposits and prepaid rent	34,624	34,064
Distributions payable	75,129	69,460
Accounts payable, accrued expenses, and other liabilities	63,857	91,282
Total liabilities	3,735,587	3,828,104
Redeemable noncontrolling interests in the Operating Partnership	311,883	282,480
Equity:
8.00% Series E Cumulative Convertible; 2,803,812 shares and outstanding at March 31, 2015 and December 31, 2014	46,571	46,571
Common stock, $0.01 par value; 350,000,000 shares authorized; 258,988,739 and 255,114,603 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	2,590	2,551
Additional paid-in capital	4,334,418	4,223,747
Distributions in excess of net income	-1,557,953	-1,528,917
Accumulated other comprehensive income/(loss), net	-15,445	-8,855
Total stockholders' equity	2,810,181	2,735,097
Noncontrolling interests	860	853
Total equity	2,811,041	2,735,950
Total liabilities and equity	$6,858,511	$6,846,534

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Real estate owned:
Real estate under development accumulated depreciation	$142	$0
Equity:
Preferred stock, par or stated value per share	$0	$0
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	350,000,000	350,000,000
Common stock, shares issued		255,114,603
Common stock, shares outstanding	258,988,739
8.00% Series E Cumulative Convertible Preferred Stock
Equity:
Preferred stock, shares outstanding	2,803,812	2,803,812

Consolidated_Balance_Sheets_UN

Consolidated Balance Sheets (UNITED DOMINION REALTY, L.P) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Real estate owned:
Real estate held for investment	$8,256,995	$8,205,627
Less: accumulated depreciation	-2,521,958	-2,434,772
Real estate held for investment, net	5,735,037	5,770,855
Real estate under development (net of accumulated depreciation of $513 and $0, respectively)	196,511	177,632
Total real estate owned, net of accumulated depreciation	5,931,548	5,948,487
Cash and cash equivalents	6,274	15,224
Deferred financing costs, net	21,676	22,686
Other assets	96,713	105,202
Total assets	6,858,511	6,846,534
LIABILITIES AND CAPITAL
Secured debt	1,370,673	1,361,529
Real estate taxes payable	21,848	15,978
Accrued interest payable	23,460	34,215
Security deposits and prepaid rent	34,624	34,064
Distributions payable	75,129	69,460
Deferred gains on the sale of depreciable property	5,600	28,500
Accounts payable, accrued expenses, and other liabilities	63,857	91,282
Total liabilities	3,735,587	3,828,104
Partners' Capital:
Accumulated other comprehensive income/(loss), net	-15,445	-8,855
Total liabilities and equity	6,858,511	6,846,534
United Dominion Reality L.P. [Member]
Real estate owned:
Real estate held for investment	4,248,795	4,238,770
Less: accumulated depreciation	-1,447,513	-1,403,303
Total real estate owned, net of accumulated depreciation	2,801,282	2,835,467
Cash and cash equivalents	826	502
Restricted Cash	14,441	13,811
Deferred financing costs, net	4,118	4,475
Other assets	22,714	24,029
Total assets	2,843,381	2,878,284
LIABILITIES AND CAPITAL
Secured debt	929,702	931,959
Notes payable due to General Partner	88,696	88,696
Real estate taxes payable	10,101	7,061
Accrued interest payable	3,243	3,284
Security deposits and prepaid rent	17,916	18,387
Distributions payable	50,962	47,788
Deferred gains on the sale of depreciable property	0	24,622
Accounts payable, accrued expenses, and other liabilities	13,903	22,436
Total liabilities	1,114,523	1,144,233
Commitments and contingencies (Note 11)
Partners' Capital:
General partner: 110,883 OP Units outstanding at March 31, 2015 and December 31, 2014	1,096	1,105
Limited partners: 183,167,815 OP Units outstanding at March 31, 2015 and December 31, 2014	1,688,364	1,702,971
Accumulated other comprehensive income/(loss), net	-840	-1,075
Total partners' capital	1,688,620	1,703,001
Advances (to)/from General Partner	22,418	13,624
Noncontrolling interests	17,820	17,426
Total capital	1,728,858	1,734,051
Total liabilities and equity	$2,843,381	$2,878,284

Consolidated_Balance_Sheets_UN1

Consolidated Balance Sheets (UNITED DOMINION REALTY, L.P) (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Real estate under development accumulated depreciation	$142	$0
United Dominion Reality L.P. [Member]
Real estate under development accumulated depreciation	$0	$0
Partners' Capital:
OP units outstanding related to general partner	110,883	110,883
OP units outstanding related to limited partner	183,167,815	183,167,815

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
REVENUES
Rental Income	$207,047,000	$194,352,000
Joint venture management and other fees	12,706,000	3,687,000
Total revenues	219,753,000	198,039,000
OPERATING EXPENSES
Property operating and maintenance	37,250,000	36,720,000
Real estate taxes and insurance	26,222,000	25,431,000
Property management	5,694,000	5,345,000
Other operating expenses	1,766,000	1,926,000
Real estate depreciation and amortization	88,777,000	88,533,000
General and administrative	12,152,000	11,994,000
Casualty-related (recoveries)/charges, net	996,000	500,000
Other depreciation and amortization	1,623,000	1,080,000
Total operating expenses	174,480,000	171,529,000
Operating income	45,273,000	26,510,000
Income/(loss) from unconsolidated entities	59,159,000	-3,565,000
Interest expense	-28,800,000	32,884,000
Interest and other income/(expense), net	360,000	1,415,000
Income/(loss) before income taxes, discountinued operations, and gain/(loss) on sale of real estate owned	75,992,000	-8,524,000
Tax benefit/(expense), net	425,000	3,329,000
Income/(loss) from continuing operations	76,417,000	-5,195,000
Income/(loss) from discontinued operations, net of tax	0	-87,000
Income/(loss) before gain/(loss) of real estate owned	76,417,000	-5,282,000
Gains/(loss) on sales of real estate, net of tax	0	24,294,000
Net income/(loss)	76,417,000	19,012,000
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership	-2,588,000	-647,000
Net (income)/loss attributable to noncontrolling interests	-7,000	-4,000
Net income/(loss) attributable to UDR, Inc.	73,822,000	18,361,000
Net (loss)/income attributable to common stockholders	72,891,000	17,430,000
Income/(loss) per weighted average common share - basic and diluted:
Income/(loss) from continuing operations attributable to common stockholders	$0.28	$0.07
Income/(loss) from discontinued operations attributable to common stockholders,	$0	$0
Net income/(loss) attributable to common stockholders	$0.28	$0.07
Income/(loss) from continuing operations attributable to common stockholders,	$0.28	$0.07
Income from discontinued operations attributable to common stockholders	$0	$0
Net income/(loss) attributable to common stockholders	$0.28	$0.07
Common distributions declared per share	$0.28	$0.26
Weighted average number of common shares outstanding b basic	256,834	250,177
Weighted average number of common shares outstanding b diluted	258,662	251,822
Series E Preferred Stock [Member]
OPERATING EXPENSES
Distributions to preferred stockholders - Series E (Convertible)	$931,000	$931,000

Consolidated_Statements_of_Ope1

Consolidated Statements of Operations (Unaudited) (UNITED DOMINION REALTY, L.P) (USD $)	3 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
OPERATING EXPENSES
Property operating and maintenance	$37,250,000	$36,720,000
Real estate taxes and insurance	26,222,000	25,431,000
Property management	5,694,000	5,345,000
Other operating expenses	1,766,000	1,926,000
Real estate depreciation and amortization	88,777,000	88,533,000
General and administrative	12,152,000	11,994,000
Casualty-related (recoveries)/charges, net	996,000	500,000
Total operating expenses	174,480,000	171,529,000
Operating income	45,273,000	26,510,000
Interest and other income/(expense), net	360,000	1,415,000
Income/(loss) from continuing operations	76,417,000	-5,195,000
Income/(loss) from discontinued operations, net of tax	0	-87,000
Gains/(loss) on sales of real estate owned	0	24,294,000
Net income/(loss)	76,417,000	19,012,000
Net (income)/loss attributable to noncontrolling interests	-2,371,000	-707,000
Net (income)/loss attributable to noncontrolling interests	-7,000	-4,000
Net income/(loss) attributable to OP unitholders	73,822,000	18,361,000
United Dominion Reality L.P. [Member]
REVENUES
Rental income	110,095,000	102,370,000
OPERATING EXPENSES
Property operating and maintenance	19,114,000	18,234,000
Real estate taxes and insurance	12,866,000	11,719,000
Property management	3,027,000	2,815,000
Other operating expenses	1,490,000	1,436,000
Real estate depreciation and amortization	44,478,000	44,271,000
General and administrative	5,639,000	6,970,000
Casualty-related (recoveries)/charges, net	593,000	500,000
Total operating expenses	87,207,000	85,945,000
Operating income	22,888,000	16,425,000
Interest expense	-9,620,000	-8,863,000
Interest expense on note payable due to General Partner	-1,151,000	-1,151,000
Income/(loss) before gain/(loss) of real estate owned	12,117,000	6,411,000
Gains/(loss) on sales of real estate owned	24,623,000	24,402,000
Net income/(loss)	36,740,000	30,813,000
Net (income)/loss attributable to noncontrolling interests	-394,000	-280,000
Net income/(loss) attributable to OP unitholders	$36,346,000	$30,533,000
Income/(loss) per OP unit- basic and diluted:
Net income/(loss) attributable to OP unitholders (in dollars per share)	$0.20	$0.17
Weighted average OP units outstanding - basic and diluted	183,279	183,279

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income / (Loss) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net income/(loss)	$76,417	$19,012
Other comprehensive income/(loss), including portion attributable to noncontrolling interests:
Unrealized holding gain/(loss)	-7,552	-55
(Gain)/loss reclassifed into earnings from other comprehensive income/(loss)	737	1,532
Other comprehensive income/(loss), including portion attributable to noncontrolling interests	-6,815	1,477
Comprehensive income/(loss)	69,602	20,489
Comprehensive (income)/loss attributable to noncontrolling interests	-2,371	-707
Comprehensive income/(loss) attributable to UDR, Inc.	$67,231	$19,782

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income / (Loss) (UNITED DOMINION REALTY, L.P.) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net income/(loss)	$76,417	$19,012
Other comprehensive income/(loss), including portion attributable to noncontrolling interests:
Unrealized holding gain/(loss)	-7,552	-55
(Gain)/loss reclassifed into earnings from other comprehensive income/(loss)	737	1,532
Other comprehensive income/(loss), including portion attributable to noncontrolling interests	-6,815	1,477
Comprehensive income/(loss)	69,602	20,489
Comprehensive (income)/loss attributable to noncontrolling interests	2,371	707
Comprehensive income/(loss) attributable to OP unitholders	67,231	19,782
United Dominion Reality L.P. [Member]
Net income/(loss)	36,740	30,813
Other comprehensive income/(loss), including portion attributable to noncontrolling interests:
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	-51	-51
(Gain)/loss reclassifed into earnings from other comprehensive income/(loss)	286	623
Other comprehensive income/(loss), including portion attributable to noncontrolling interests	235	572
Comprehensive income/(loss)	36,975	31,385
Comprehensive (income)/loss attributable to noncontrolling interests	394	280
Comprehensive income/(loss) attributable to OP unitholders	$36,581	$31,105

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Equity (Unaudited) (USD $)	Total	Preferred Stock [Member]	Common Stock [Member]	Paid - in Capital	Distributions in Excess of Net Income	Accumulated Other Comprehensive Income/(Loss)	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2014	$2,735,950,000	$46,571,000	$2,551,000	$4,223,747,000	($1,528,917,000)	($8,855,000)	$853,000
Beginning Balance, Shares at Dec. 31, 2014		2,803,812	255,114,603
Stock Redeemed or Called During Period, Value		0			0
Stock Issued During Period, Shares, New Issues			3,439,636
Stock Issued During Period, Shares, Conversion of Units			534
Consolidted Statements of Changes in Equity
Net income/(loss) attributable to UDR, Inc.	73,822,000
Net income/(loss) attributable to noncontrolling interests	7,000						7,000
Other comprehensive income/(loss)	-6,590,000					-6,590,000
Issuance/(forfeiture) of common and restricted shares, net Shares			-433,966
Issuance/(forfeitures) of common and restricted shares, net	1,903,000		4,000	1,899,000
Issuance of common shares through public offering	108,790,000		34,000	108,756,000
Adjustment for conversion of noncontrolling interest of unitholders in Operating Partnership	17,000		-1,000	-16,000
Common stock distributions declared ($0.2775 per share)	72,231,000				72,231,000
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests							0
Preferred stock distributions declared-Series E ($0.3322 per share)	931,000				931,000
Adjustment to reflect redemption value of redeemable noncontrolling interests	-29,696,000				-29,696,000
Stock Redeemed or Called During Period, Shares		0
Ending Balance at Mar. 31, 2015	$2,811,041,000	$46,571,000	$2,590,000	$4,334,418,000	($1,557,953,000)	($15,445,000)	$860,000
Ending Balance, Shares at Mar. 31, 2015		2,803,812	258,988,739

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Equity (Unaudited) (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2015
Common distributions declared per share	$0.28
Series E Preferred Stock [Member]
Preferred stock distributions declared	$0.33

Consolidated_Statements_of_Cha2

Consolidated Statements of Changes in Capital (UNITED DOMINION REALTY, L.P) (Unaudited) (United Dominion Reality L.P. [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Balance, December 31, 2014	$1,734,051
Advances (to)/from General Partner	-22,418
Net income/(loss)	36,740
Distributions	50,962
OP Unit Redemptions for common shares of UDR	0
Adjustment to reflect limited partners' capital at redemption value	0
Unrealized Gain (Loss) on Derivatives	235
Net change in amount due to/(from) General Partner	8,794
Balance, March 31, 2015	1,728,858
Payable/(Receivable) due to/(from) General Partner [Member] [Member]
Net change in amount due to/(from) General Partner	8,794
Accumulated Other Comprehensive Income (Loss) [Member]
Balance, December 31, 2014	-1,075
Unrealized Gain (Loss) on Derivatives	235
Balance, March 31, 2015	-840
Total Partner's Capital [Member]
Balance, December 31, 2014	1,703,001
Net income/(loss)	36,346
Distributions	50,962
Adjustment to reflect limited partners' capital at redemption value	0
Balance, March 31, 2015	1,688,620
Noncontrolling Interest [Member]
Balance, December 31, 2014	17,426
Net income/(loss)	394
Balance, March 31, 2015	17,820
Partnership Capital [Member]
OP Unit Redemptions for common shares of UDR	0
Unrealized Gain (Loss) on Derivatives	235
Class A Limited Partner [Member]
Balance, December 31, 2014	53,987
Net income/(loss)	415
Distributions	-582
Adjustment to reflect limited partners' capital at redemption value	5,789
Balance, March 31, 2015	59,609
Limited Partners [Member]
Balance, December 31, 2014	228,493
Net income/(loss)	1,467
Distributions	-2,057
OP Unit Redemptions for common shares of UDR	-16
Adjustment to reflect limited partners' capital at redemption value	24,387
Balance, March 31, 2015	252,274
Limited Partner [Member]
Balance, December 31, 2014	1,420,491
Net income/(loss)	34,442
Distributions	-48,292
OP Unit Redemptions for common shares of UDR	16
Adjustment to reflect limited partners' capital at redemption value	-30,176
Balance, March 31, 2015	1,376,481
General Partner [Member]
Balance, December 31, 2014	1,105
Net income/(loss)	22
Distributions	-31
Balance, March 31, 2015	$1,096

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating Activities
Net income/(loss)	$76,417	$19,012
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	90,400	89,613
Gain on sale of real estate owned, net of tax	0	-24,294
Tax (benefit)/provision, net	-425	-3,329
Income/(loss) from unconsolidated entities	-59,159	3,565
Fee Income from the Sale of Real Estate	-9,634	0
Casualty-related (recoveries)/charges, net	996	500
Other	6,324	6,697
Changes in operating assets and liabilities:
(Increase)/decrease in operating assets	4,794	8,422
Increase/(decrease) in operating liabilities	-23,329	-17,665
Net cash provided by operating activities	96,018	82,521
Investing Activities
Acquisition of real estate assets	0	-77,793
Proceeds from sales of real estate investments, net	0	47,922
Development of real estate assets	-43,563	-56,147
Capital expenditures and other major improvements - real estate assets, net of escrow reimbursement	-20,431	-30,226
Capital expenditures - non-real estate assets	-437	-1,115
Investment in unconsolidated joint ventures	-25,463	-21,476
Distributions received from unconsolidated joint venture	41,481	7,661
Purchase deposits on pending acquisitions	0	-4,000
(Issuance)/repayment of notes receivable	-1,125	-1,535
Net cash provided by/(used in) investing activities	-49,538	-136,709
Financing Activities
Payments on secured debt	-2,266	-2,486
Proceeds from the issuance of secured debt	0	4,553
Payments on unsecured debt	-325,211	-184,000
Net proceeds/(repayment) of revolving bank debt	236,500	287,500
Proceeds from the issuance of common shares through public offering, net	108,790	0
Distributions paid to redeemable noncontrolling interests	-2,509	-2,360
Distributions paid to preferred stockholders	-931	-931
Distributions paid to common stockholders	-66,692	-58,952
Other	-3,111	-3,494
Net cash provided by/(used in) financing activities	-55,430	39,830
Net increase/(decrease) in cash and cash equivalents	-8,950	-14,358
Cash and cash equivalents, beginning of period	15,224	30,249
Cash and cash equivalents, end of period	6,274	15,891
Supplemental Information:
Interest paid during the period, net of amounts capitalized	40,282	38,180
Non-cash transactions:
Acquisition of real estate	24,067	0
Fair value adjustment of debt acquired as part of acquisition of real estate	$1,363	$0

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (UNITED DOMINION REALTY, L.P) (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating Activities
Net income/(loss)	$76,417	$19,012
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	90,400	89,613
Gain/(loss) on sale of real estate owned	0	-24,294
Casualty-related (recoveries)/charges, net	996	500
Other	6,324	6,697
Changes in operating assets and liabilities:
(Increase)/decrease in operating assets	4,794	8,422
Increase/(decrease) in operating liabilities	-23,329	-17,665
Net cash provided by operating activities	96,018	82,521
Investing Activities
Development of real estate assets	-43,563	-56,147
Capital expenditures and other major improvements - real estate assets, net of escrow reimbursement	-20,431	-30,226
Net cash provided by/(used in) investing activities	-49,538	-136,709
Financing Activities
Proceeds from the issuance of secured debt	0	4,553
Payments on secured debt	-2,266	-2,486
Net cash provided by/(used in) financing activities	-55,430	39,830
Net increase/(decrease) in cash and cash equivalents	-8,950	-14,358
Cash and cash equivalents, beginning of period	15,224	30,249
Cash and cash equivalents, end of period	6,274	15,891
Supplemental Information:
Interest paid during the period, net of amounts capitalized	40,282	38,180
United Dominion Reality L.P. [Member]
Operating Activities
Net income/(loss)	36,740	30,813
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	44,478	44,271
Gain/(loss) on sale of real estate owned	-24,623	-24,402
Casualty-related (recoveries)/charges, net	593	500
Other	-108	32
Changes in operating assets and liabilities:
(Increase)/decrease in operating assets	342	1,510
Increase/(decrease) in operating liabilities	100	-4,052
Net cash provided by operating activities	57,522	48,672
Investing Activities
Proceeds from sale of real estate investments, net	0	47,922
Development of real estate assets	-7,141	-9,860
Capital expenditures and other major improvements - real estate assets, net of escrow reimbursement	-9,761	-9,181
Net cash provided by/(used in) investing activities	-16,902	28,881
Financing Activities
Advances from/(to) General Partner, net	-36,485	-74,963
Payments on secured debt	-1,302	-1,274
Distributions paid to partnership unitholders	-2,509	-2,360
Net cash provided by/(used in) financing activities	-40,296	-78,597
Net increase/(decrease) in cash and cash equivalents	324	-1,044
Cash and cash equivalents, beginning of period	502	1,897
Cash and cash equivalents, end of period	826	853
Supplemental Information:
Interest paid during the period, net of amounts capitalized	$11,471	$10,742

Consolidation_and_Basis_of_Pre

Consolidation and Basis of Presentation	3 Months Ended
Consolidation and Basis of Presentation	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
CONSOLIDATION AND BASIS OF PRESENTATION	CONSOLIDATION AND BASIS OF PRESENTATION
	Consolidation and Basis of Presentation
	UDR, Inc., collectively with our consolidated subsidiaries (“UDR,” the “Company,” “we,” “our,” or “us”), is a self-administered real estate investment trust, or REIT, that owns, operates, acquires, renovates, develops, redevelops, and manages apartment communities. The accompanying consolidated financial statements include the accounts of UDR and its subsidiaries, including United Dominion Realty, L.P. (the “Operating Partnership” or the “OP”). As of March 31, 2015, there were 183,278,698 units in the Operating Partnership outstanding, of which 174,113,759 units, or 95.0%, were owned by UDR and 9,164,939 units, or 5.0%, were owned by limited partners. The consolidated financial statements of UDR include the noncontrolling interests of the unitholders in the Operating Partnership.
	The accompanying interim unaudited consolidated financial statements have been prepared according to the rules and regulations of the Securities and Exchange Commission. Certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been condensed or omitted according to such rules and regulations, although management believes that the disclosures are adequate to make the information presented not misleading. In the opinion of management, all adjustments and eliminations necessary for the fair presentation of our financial position as of March 31, 2015, and results of operations for the three months ended March 31, 2015 and 2014 have been included. Such adjustments are normal and recurring in nature. The interim results presented are not necessarily indicative of results that can be expected for a full year. The accompanying interim unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes for the year ended December 31, 2014 appearing in UDR’s Annual Report on Form 10-K, filed with the Securities and Exchange Commission on February 24, 2015.
	The accompanying interim unaudited consolidated financial statements are presented in accordance with U.S. generally accepted accounting principles (“GAAP”). GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities at the dates of the interim unaudited consolidated financial statements and the amounts of revenues and expenses during the reporting periods. Actual amounts realized or paid could differ from those estimates. All significant intercompany accounts and transactions have been eliminated in consolidation.
	The Company evaluated subsequent events through the date its financial statements were issued. No significant recognized or non-recognized subsequent events were noted.

Consolidation_and_Basis_of_Pre1

Consolidation and Basis of Presentation (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
CONSOLIDATION AND BASIS OF PRESENTATION	CONSOLIDATION AND BASIS OF PRESENTATION
	Consolidation and Basis of Presentation
	UDR, Inc., collectively with our consolidated subsidiaries (“UDR,” the “Company,” “we,” “our,” or “us”), is a self-administered real estate investment trust, or REIT, that owns, operates, acquires, renovates, develops, redevelops, and manages apartment communities. The accompanying consolidated financial statements include the accounts of UDR and its subsidiaries, including United Dominion Realty, L.P. (the “Operating Partnership” or the “OP”). As of March 31, 2015, there were 183,278,698 units in the Operating Partnership outstanding, of which 174,113,759 units, or 95.0%, were owned by UDR and 9,164,939 units, or 5.0%, were owned by limited partners. The consolidated financial statements of UDR include the noncontrolling interests of the unitholders in the Operating Partnership.
	The accompanying interim unaudited consolidated financial statements have been prepared according to the rules and regulations of the Securities and Exchange Commission. Certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been condensed or omitted according to such rules and regulations, although management believes that the disclosures are adequate to make the information presented not misleading. In the opinion of management, all adjustments and eliminations necessary for the fair presentation of our financial position as of March 31, 2015, and results of operations for the three months ended March 31, 2015 and 2014 have been included. Such adjustments are normal and recurring in nature. The interim results presented are not necessarily indicative of results that can be expected for a full year. The accompanying interim unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes for the year ended December 31, 2014 appearing in UDR’s Annual Report on Form 10-K, filed with the Securities and Exchange Commission on February 24, 2015.
	The accompanying interim unaudited consolidated financial statements are presented in accordance with U.S. generally accepted accounting principles (“GAAP”). GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities at the dates of the interim unaudited consolidated financial statements and the amounts of revenues and expenses during the reporting periods. Actual amounts realized or paid could differ from those estimates. All significant intercompany accounts and transactions have been eliminated in consolidation.
	The Company evaluated subsequent events through the date its financial statements were issued. No significant recognized or non-recognized subsequent events were noted.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
CONSOLIDATION AND BASIS OF PRESENTATION	CONSOLIDATION AND BASIS OF PRESENTATION
	Consolidation and Basis of Presentation
	United Dominion Realty, L.P. (“UDR, L.P.,” the “Operating Partnership,” “we” or “our”) is a Delaware limited partnership, that owns, acquires, renovates, redevelops, manages, and disposes of multifamily apartment communities generally located in high barrier to entry markets located in the United States. The high barrier to entry markets are characterized by limited land for new construction, difficult and lengthy entitlement process, expensive single-family home prices and significant employment growth potential. UDR, L.P. is a subsidiary of UDR, Inc. (“UDR” or the “General Partner”), a self-administered real estate investment trust, or REIT, through which UDR conducts a significant portion of its business. During the three months ended March 31, 2015 and 2014, rental revenues of the Operating Partnership represented 53% of the General Partner’s consolidated rental revenues. As of March 31, 2015, the Operating Partnership’s apartment portfolio consisted of 68 communities located in 17 markets consisting of 20,809 apartment homes.
	Interests in UDR, L.P. are represented by operating partnership units (“OP Units”). The Operating Partnership’s net income is allocated to the partners, which is initially based on their respective distributions made during the year and secondly, their percentage interests. Distributions are made in accordance with the terms of the Amended and Restated Agreement of Limited Partnership of United Dominion Realty, L.P. (the “Operating Partnership Agreement”), on a per unit basis that is generally equal to the dividend per share on UDR’s common stock, which is publicly traded on the New York Stock Exchange (“NYSE”) under the ticker symbol “UDR.”
	As of March 31, 2015, there were 183,278,698 OP Units outstanding, of which 174,113,759 or 95.0% were owned by UDR and affiliated entities and 9,164,939 or 5.0% were owned by non-affiliated limited partners. See Note 8, Capital Structure.
	The accompanying interim unaudited consolidated financial statements have been prepared according to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been condensed or omitted according to such rules and regulations, although management believes that the disclosures are adequate to make the information presented not misleading. In the opinion of management, all adjustments and eliminations necessary for the fair presentation of our financial position as of March 31, 2015, and results of operations for the three months ended March 31, 2015 and 2014 have been included. Such adjustments are normal and recurring in nature. The interim results presented are not necessarily indicative of results that can be expected for a full year. The accompanying interim unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes for the year ended March 31, 2015 included in the Annual Report on Form 10-K filed by UDR and the Operating Partnership with the SEC on February 24, 2015.
	The accompanying interim unaudited consolidated statements are presented in accordance with U.S. generally accepted accounting principles (“GAAP”). GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities at the dates of the interim unaudited consolidated financial statements and the amounts of revenues and expenses during the reporting periods. Actual amounts realized or paid could differ from those estimates. All intercompany accounts and transactions have been eliminated in consolidation.
	The Operating Partnership evaluated subsequent events through the date its financial statements were issued. No recognized or non-recognized subsequent events were noted.

Significant_Accounting_Policie

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The standard specifically excludes lease contracts. The ASU allows for the use of either the full or modified retrospective transition method, and the standard will be effective for the Company on January 1, 2017; early adoption is not permitted. The Company has not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.
	Discontinued Operations
	In accordance with GAAP, a discontinued operation represents (1) a component of an entity or group of components that has been disposed of or is classified as held for sale in a single transaction and represents a strategic shift that has or will have a major effect on an entity’s financial results, or (2) an acquired business that is classified as held for sale on the date of acquisition. A strategic shift could include a disposal of (1) a separate major line of business, (2) a separate major geographic area of operations, (3) a major equity method investment, or (4) other major parts of an entity.
	We record sales of real estate that do not meet the definition of a discontinued operation in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations.
	Revenue and Real Estate Sales Gain Recognition
	Rental income related to leases is recognized on an accrual basis when due from residents and tenants in accordance with GAAP. Rental payments are generally due on a monthly basis and recognized when earned. The Company recognizes interest income, management and other fees and incentives when earned, and the amounts are fixed and determinable.
	For sale transactions meeting the requirements for full accrual profit recognition, we remove the related assets and liabilities from our Consolidated Balance Sheets and record the gain or loss in the period the transaction closes. For sale transactions that do not meet the full accrual sale criteria due to our continuing involvement, we evaluate the nature of the continuing involvement and account for the transaction under an alternate method of accounting. Unless certain limited criteria are met, non-monetary transactions, including property exchanges, are accounted for at fair value.
	Sales to entities in which we retain or otherwise own an interest are accounted for as partial sales. If all other requirements for recognizing profit under the full accrual method have been satisfied and no other forms of continuing involvement are present, we recognize profit proportionate to the outside interest in the buyer and defer the gain on the interest we retain. The Company recognizes any deferred gain when the property is sold to a third party. In transactions accounted for by us as partial sales, we determine if the buyer of the majority equity interest in the venture was provided a preference as to cash flows in either an operating or a capital waterfall. If a cash flow preference has been provided, we recognize profit only to the extent that proceeds from the sale of the majority equity interest exceed costs related to the entire property.
	Notes Receivable

	The following table summarizes our notes receivable, net as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Interest rate at		Balance outstanding
		March 31,		March 31,		December 31, 2014
		2015		2015
	Note due February 2017 (a)	10	%	$	12,994	$	11,869

	Note due July 2017 (b)	8	%	2,500		2,500

	Total notes receivable, net			$	15,494	$	14,369

	(a) The Company has a secured note receivable with an unaffiliated third party with an aggregate commitment of $13.0 million. During the three months ended March 31, 2015, the Company loaned an additional $1.1 million. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) the fifth anniversary of the date of the note (February 2017).
	(b) The Company has a secured note receivable with an unaffiliated third party with an aggregate commitment of $2.5 million. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) the fifth anniversary of the date of the note (July 2017).
	The Company recognized $0.4 million and $1.2 million of interest income from notes receivable during the three months ended March 31, 2015 and 2014, respectively, none of which was related party interest income. Interest income is included in Interest and other income/(expense), net on the Consolidated Statements of Operations.
	Comprehensive Income/(Loss)
	Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to stockholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three months ended March 31, 2015 and 2014, the Company’s other comprehensive income/(loss) consisted of the gain/(loss) (effective portion) on derivative instruments that are designated as and qualify as cash flow hedges, (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) into earnings, and the allocation of other comprehensive income/(loss) to redeemable noncontrolling interests. The (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) is included in Interest expense on the Consolidated Statements of Operations. See Note 10, Derivatives and Hedging Activity, for further discussion. The allocation of other comprehensive income/(loss) to redeemable noncontrolling interests was $(225,000) and $56,000 during the three months ended March 31, 2015 and 2014, respectively.
	Income Taxes
	Due to the structure of the Company as a REIT and the nature of the operations for the operating properties, no provision for federal income taxes has been provided for at UDR. Historically, the Company has generally incurred only state and local excise and franchise taxes. UDR has elected for certain consolidated subsidiaries to be treated as taxable REIT subsidiaries (“TRS”), primarily those engaged in development activities.
	Income taxes for our TRS are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rate is recognized in earnings in the period of the enactment date. The Company’s deferred tax assets are generally the result of differing depreciable lives on capitalized assets and timing of expense recognition for certain accrued liabilities. As of March 31, 2015, UDR’s net deferred tax asset was $7.6 million (net of a valuation allowance of less than $0.1 million), which is included in Other assets on the Consolidated Balance Sheets.
	GAAP defines a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. GAAP also provides guidance on derecognition, classification, interest and penalties, accounting for interim periods, disclosure and transition.
	The Company recognizes its tax positions and evaluates them using a two-step process. First, UDR determines whether a tax position is more likely than not (greater than 50 percent probability) to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Second, the Company will determine the amount of benefit to recognize and record the amount that is more likely than not to be realized upon ultimate settlement.
	UDR had no material unrecognized tax benefit, accrued interest or penalties at March 31, 2015. UDR and its subsidiaries are subject to federal income tax as well as income tax of various state and local jurisdictions. The tax years 2010 through 2013 remain open to examination by tax jurisdictions to which we are subject. When applicable, UDR recognizes interest and/or penalties related to uncertain tax positions in Tax benefit/(expense), net on the Consolidated Statements of Operations.

Significant_Accounting_Policie1

Significant Accounting Policies (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The standard specifically excludes lease contracts. The ASU allows for the use of either the full or modified retrospective transition method, and the standard will be effective for the Company on January 1, 2017; early adoption is not permitted. The Company has not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.
	Discontinued Operations
	In accordance with GAAP, a discontinued operation represents (1) a component of an entity or group of components that has been disposed of or is classified as held for sale in a single transaction and represents a strategic shift that has or will have a major effect on an entity’s financial results, or (2) an acquired business that is classified as held for sale on the date of acquisition. A strategic shift could include a disposal of (1) a separate major line of business, (2) a separate major geographic area of operations, (3) a major equity method investment, or (4) other major parts of an entity.
	We record sales of real estate that do not meet the definition of a discontinued operation in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations.
	Revenue and Real Estate Sales Gain Recognition
	Rental income related to leases is recognized on an accrual basis when due from residents and tenants in accordance with GAAP. Rental payments are generally due on a monthly basis and recognized when earned. The Company recognizes interest income, management and other fees and incentives when earned, and the amounts are fixed and determinable.
	For sale transactions meeting the requirements for full accrual profit recognition, we remove the related assets and liabilities from our Consolidated Balance Sheets and record the gain or loss in the period the transaction closes. For sale transactions that do not meet the full accrual sale criteria due to our continuing involvement, we evaluate the nature of the continuing involvement and account for the transaction under an alternate method of accounting. Unless certain limited criteria are met, non-monetary transactions, including property exchanges, are accounted for at fair value.
	Sales to entities in which we retain or otherwise own an interest are accounted for as partial sales. If all other requirements for recognizing profit under the full accrual method have been satisfied and no other forms of continuing involvement are present, we recognize profit proportionate to the outside interest in the buyer and defer the gain on the interest we retain. The Company recognizes any deferred gain when the property is sold to a third party. In transactions accounted for by us as partial sales, we determine if the buyer of the majority equity interest in the venture was provided a preference as to cash flows in either an operating or a capital waterfall. If a cash flow preference has been provided, we recognize profit only to the extent that proceeds from the sale of the majority equity interest exceed costs related to the entire property.
	Notes Receivable

	The following table summarizes our notes receivable, net as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Interest rate at		Balance outstanding
		March 31,		March 31,		December 31, 2014
		2015		2015
	Note due February 2017 (a)	10	%	$	12,994	$	11,869

	Note due July 2017 (b)	8	%	2,500		2,500

	Total notes receivable, net			$	15,494	$	14,369

	(a) The Company has a secured note receivable with an unaffiliated third party with an aggregate commitment of $13.0 million. During the three months ended March 31, 2015, the Company loaned an additional $1.1 million. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) the fifth anniversary of the date of the note (February 2017).
	(b) The Company has a secured note receivable with an unaffiliated third party with an aggregate commitment of $2.5 million. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) the fifth anniversary of the date of the note (July 2017).
	The Company recognized $0.4 million and $1.2 million of interest income from notes receivable during the three months ended March 31, 2015 and 2014, respectively, none of which was related party interest income. Interest income is included in Interest and other income/(expense), net on the Consolidated Statements of Operations.
	Comprehensive Income/(Loss)
	Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to stockholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three months ended March 31, 2015 and 2014, the Company’s other comprehensive income/(loss) consisted of the gain/(loss) (effective portion) on derivative instruments that are designated as and qualify as cash flow hedges, (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) into earnings, and the allocation of other comprehensive income/(loss) to redeemable noncontrolling interests. The (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) is included in Interest expense on the Consolidated Statements of Operations. See Note 10, Derivatives and Hedging Activity, for further discussion. The allocation of other comprehensive income/(loss) to redeemable noncontrolling interests was $(225,000) and $56,000 during the three months ended March 31, 2015 and 2014, respectively.
	Income Taxes
	Due to the structure of the Company as a REIT and the nature of the operations for the operating properties, no provision for federal income taxes has been provided for at UDR. Historically, the Company has generally incurred only state and local excise and franchise taxes. UDR has elected for certain consolidated subsidiaries to be treated as taxable REIT subsidiaries (“TRS”), primarily those engaged in development activities.
	Income taxes for our TRS are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rate is recognized in earnings in the period of the enactment date. The Company’s deferred tax assets are generally the result of differing depreciable lives on capitalized assets and timing of expense recognition for certain accrued liabilities. As of March 31, 2015, UDR’s net deferred tax asset was $7.6 million (net of a valuation allowance of less than $0.1 million), which is included in Other assets on the Consolidated Balance Sheets.
	GAAP defines a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. GAAP also provides guidance on derecognition, classification, interest and penalties, accounting for interim periods, disclosure and transition.
	The Company recognizes its tax positions and evaluates them using a two-step process. First, UDR determines whether a tax position is more likely than not (greater than 50 percent probability) to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Second, the Company will determine the amount of benefit to recognize and record the amount that is more likely than not to be realized upon ultimate settlement.
	UDR had no material unrecognized tax benefit, accrued interest or penalties at March 31, 2015. UDR and its subsidiaries are subject to federal income tax as well as income tax of various state and local jurisdictions. The tax years 2010 through 2013 remain open to examination by tax jurisdictions to which we are subject. When applicable, UDR recognizes interest and/or penalties related to uncertain tax positions in Tax benefit/(expense), net on the Consolidated Statements of Operations.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The standard specifically excludes lease contracts. The ASU allows for the use of either the full or modified retrospective transition method, and the standard will be effective for the Operating Partnership on January 1, 2017; early adoption is not permitted. The Operating Partnership has not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures.
	Discontinued Operations
	In accordance with GAAP, a discontinued operation represents (1) a component of an entity or group of components that has been disposed of or is classified as held for sale in a single transaction and represents a strategic shift that has or will have a major effect on an entity’s financial results, or (2) an acquired business that is classified as held for sale on the date of acquisition. A strategic shift could include a disposal of (1) a separate major line of business, (2) a separate major geographic area of operations, (3) a major equity method investment, or (4) other major parts of an entity.
	We record sales of real estate that do not meet the definition of a discontinued operation in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations.

	Income/(Loss) Per Operating Partnership Unit
	Basic income/(loss) per OP Unit is computed by dividing net income/(loss) attributable to general and limited partner unitholders by the weighted average number of general and limited partner units outstanding during the year. Diluted income/(loss) per OP Unit reflects the potential dilution that could occur if securities or other contracts to issue OP Units were exercised or converted into OP Units or resulted in the issuance of OP Units and then shared in the income/(loss) of the Operating Partnership.
	Revenue and Real Estate Sales Gain Recognition
	Rental income related to leases is recognized on an accrual basis when due from residents and tenants in accordance with GAAP. Rental payments are generally due on a monthly basis and recognized when earned. The Operating Partnership recognizes interest income, fees and incentives when earned, fixed and determinable.
	For sale transactions meeting the requirements for full accrual profit recognition, we remove the related assets and liabilities from our Consolidated Balance Sheets and record the gain or loss in the period the transaction closes. For sale transactions that do not meet the full accrual sale criteria due to our continuing involvement, we evaluate the nature of the continuing involvement and account for the transaction under an alternate method of accounting. Unless certain limited criteria are met, non-monetary transactions, including property exchanges, are accounted for at fair value.
	Sales to entities in which we or our General Partner retain or otherwise own an interest are accounted for as partial sales. If all other requirements for recognizing profit under the full accrual method have been satisfied and no other forms of continuing involvement are present, we recognize profit proportionate to the outside interest in the buyer and defer the gain on the interest we or our General Partner retain. The Operating Partnership recognizes any deferred gain when the property is sold to a third party. In transactions accounted by us as partial sales, we determine if the buyer of the majority equity interest in the venture was provided a preference as to cash flows in either an operating or a capital waterfall. If a cash flow preference has been provided, we recognize profit only to the extent that proceeds from the sale of the majority equity interest exceed costs related to the entire property.
	Comprehensive Income/(Loss)
	Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to unitholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three months ended March 31, 2015 and 2014, the Operating Partnership’s other comprehensive income/(loss) consisted of the gain/(loss) (effective portion) on derivative instruments that are designated as and qualify as cash flow hedges and (gain)/loss reclassified from other comprehensive income/(loss) into earnings. The (gain)/loss reclassified from other comprehensive income/(loss) is included in Interest expense on the Consolidated Statements of Operations. See Note 7, Derivatives and Hedging Activity, for further discussion.
	Income Taxes
	The taxable income or loss of the Operating Partnership is reported on the tax returns of the partners. Accordingly, no provision has been made in the accompanying financial statements for federal or state income taxes on income that is passed through to the partners. However, any state or local revenue, excise or franchise taxes that result from the operating activities of the Operating Partnership are recorded at the entity level. The Operating Partnership’s tax returns are subject to examination by federal and state taxing authorities. Net income for financial reporting purposes differs from the net income for income tax reporting purposes primarily due to temporary differences, principally real estate depreciation and the tax deferral of certain gains on property sales. The differences in depreciation result from differences in the book and tax basis of certain real estate assets and the differences in the methods of depreciation and lives of the real estate assets.
	The Operating Partnership evaluates the accounting and disclosure of tax positions taken or expected to be taken in the course of preparing the Operating Partnership’s tax returns to determine whether the tax positions are “more-likely-than-not” of being sustained by the applicable tax authority. Tax positions not deemed to meet the more-likely-than-not threshold would be recorded as a tax benefit or expense in the current year. Management of the Operating Partnership is required to analyze all open tax years, as defined by the statute of limitations, for all major jurisdictions, which include federal and certain states. The Operating Partnership has no examinations in progress and none are expected at this time.
	Management of the Operating Partnership has reviewed all open tax years (2010 through 2013) of tax jurisdictions and concluded there is no tax liability resulting from unrecognized tax benefits relating to uncertain income tax positions taken or expected to be taken in future tax returns.

Real_Estate_Owned

Real Estate Owned	3 Months Ended
	Mar. 31, 2015
Real Estate [Abstract]
REAL ESTATE OWNED	REAL ESTATE OWNED
	Real estate assets owned by the Company consist of income producing operating properties, properties under development, land held for future development, and sold or held for disposition properties. As of March 31, 2015, the Company owned and consolidated 138 communities in 10 states plus the District of Columbia totaling 39,956 apartment homes. The following table summarizes the carrying amounts for our real estate owned (at cost) as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Land and land improvements	$	1,984,019		$	1,980,221

	Depreciable property — held and used:
	Building, improvements, and furniture, fixtures and equipment	6,272,976			6,225,406

	Under development:
	Land and land improvements	24,584			24,584

	Building, improvements, and furniture, fixtures and equipment	172,069			153,048

	Real estate owned	8,453,648			8,383,259

	Accumulated depreciation	(2,522,100		)	(2,434,772		)
	Real estate owned, net	$	5,931,548		$	5,948,487


	In February 2015, the Company acquired an office building in Highlands Ranch, Colorado, for total consideration of approximately $24.0 million, which was comprised of assumed debt. The Company's corporate offices, as well as other leased office space, are located in the acquired building. The building consists of approximately 120,000 square feet, of which UDR occupies approximately 44,000 square feet. All existing leases were assumed by the Company at the time of acquisition.

	During the three months ended March 31, 2015, the Company did not sell or have any properties classified as held for sale.

	Predevelopment, development, and redevelopment projects and related costs are capitalized and reported on the Consolidated Balance Sheets as Total real estate owned, net of accumulated depreciation. The Company capitalizes costs directly related to the predevelopment, development, and redevelopment of a capital project, which include, but are not limited to, interest, real estate taxes, insurance, and allocated development and redevelopment overhead related to support costs for personnel working on the capital projects. We use our professional judgment in determining whether such costs meet the criteria for capitalization or must be expensed as incurred. These costs are capitalized only during the period in which activities necessary to ready an asset for its intended use are in progress and such costs are incremental and identifiable to a specific activity to get the asset ready for its intended use. These costs, excluding the direct costs of development and redevelopment and capitalized interest, were $2.2 million and $3.4 million for the three months ended March 31, 2015 and 2014, respectively. Total interest capitalized was $4.8 million and $5.3 million for the three months ended March 31, 2015 and 2014, respectively. As each home in a capital project is completed and becomes available for lease-up, the Company ceases capitalization on the related portion and depreciation commences over the estimated useful life.

	During the three months ended March 31, 2015, the Company recorded a loss of of $996,000 related to damage caused by severe snow storms to properties located on the east coast, which is included in Casualty-related (recoveries)/charges, net on the Consolidated Statements of Operations.

Real_Estate_Owned_UNITED_DOMIN

Real Estate Owned (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
REAL ESTATE OWNED	REAL ESTATE OWNED
	Real estate assets owned by the Company consist of income producing operating properties, properties under development, land held for future development, and sold or held for disposition properties. As of March 31, 2015, the Company owned and consolidated 138 communities in 10 states plus the District of Columbia totaling 39,956 apartment homes. The following table summarizes the carrying amounts for our real estate owned (at cost) as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Land and land improvements	$	1,984,019		$	1,980,221

	Depreciable property — held and used:
	Building, improvements, and furniture, fixtures and equipment	6,272,976			6,225,406

	Under development:
	Land and land improvements	24,584			24,584

	Building, improvements, and furniture, fixtures and equipment	172,069			153,048

	Real estate owned	8,453,648			8,383,259

	Accumulated depreciation	(2,522,100		)	(2,434,772		)
	Real estate owned, net	$	5,931,548		$	5,948,487


	In February 2015, the Company acquired an office building in Highlands Ranch, Colorado, for total consideration of approximately $24.0 million, which was comprised of assumed debt. The Company's corporate offices, as well as other leased office space, are located in the acquired building. The building consists of approximately 120,000 square feet, of which UDR occupies approximately 44,000 square feet. All existing leases were assumed by the Company at the time of acquisition.

	During the three months ended March 31, 2015, the Company did not sell or have any properties classified as held for sale.

	Predevelopment, development, and redevelopment projects and related costs are capitalized and reported on the Consolidated Balance Sheets as Total real estate owned, net of accumulated depreciation. The Company capitalizes costs directly related to the predevelopment, development, and redevelopment of a capital project, which include, but are not limited to, interest, real estate taxes, insurance, and allocated development and redevelopment overhead related to support costs for personnel working on the capital projects. We use our professional judgment in determining whether such costs meet the criteria for capitalization or must be expensed as incurred. These costs are capitalized only during the period in which activities necessary to ready an asset for its intended use are in progress and such costs are incremental and identifiable to a specific activity to get the asset ready for its intended use. These costs, excluding the direct costs of development and redevelopment and capitalized interest, were $2.2 million and $3.4 million for the three months ended March 31, 2015 and 2014, respectively. Total interest capitalized was $4.8 million and $5.3 million for the three months ended March 31, 2015 and 2014, respectively. As each home in a capital project is completed and becomes available for lease-up, the Company ceases capitalization on the related portion and depreciation commences over the estimated useful life.

	During the three months ended March 31, 2015, the Company recorded a loss of of $996,000 related to damage caused by severe snow storms to properties located on the east coast, which is included in Casualty-related (recoveries)/charges, net on the Consolidated Statements of Operations.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
REAL ESTATE OWNED	REAL ESTATE OWNED
	Real estate assets owned by the Operating Partnership consists of income producing operating properties, properties under development, land held for future development, and sold or held for disposition properties. As of March 31, 2015, the Operating Partnership owned and consolidated 68 communities in nine states plus the District of Columbia totaling 20,809 apartment homes. The following table summarizes the carrying amounts for our real estate owned (at cost) as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Land	$	1,008,358		$	1,008,014

	Depreciable property — held and used:
	Buildings, improvements, and furniture, fixture and equipment	3,240,437			3,230,756

	Real estate owned	4,248,795			4,238,770

	Accumulated depreciation	(1,447,513		)	(1,403,303		)
	Real estate owned, net	$	2,801,282		$	2,835,467

	The Operating Partnership did not have any acquisitions or real estate sales during the three months ended March 31, 2015.
	Predevelopment, development, and redevelopment projects and related costs are capitalized and reported on the Consolidated Balance Sheets as Total real estate owned, net of accumulated depreciation. The Operating Partnership capitalizes costs directly related to the predevelopment, development, and redevelopment of a capital project, which include, but are not limited to, interest, real estate taxes, insurance, and allocated development and redevelopment overhead related to support costs for personnel working on the capital projects. We use our professional judgment in determining whether such costs meet the criteria for capitalization or must be expensed as incurred. These costs are capitalized only during the period in which activities necessary to ready an asset for its intended use are in progress and such costs are incremental and identifiable to a specific activity to get the asset ready for its intended use. These costs, excluding the direct costs of development and redevelopment and capitalized interest, were $133,000 and $1.0 million for the three months ended March 31, 2015 and 2014, respectively. Total interest capitalized was $22,000 and $755,000 during the three months ended March 31, 2015 and 2014, respectively. As each home in a capital project is completed and becomes available for lease-up, the Company ceases capitalization on the related portion and depreciation commences over the estimated useful life.

	During the three months ended March 31, 2015, the Company recorded a loss of of $593,000 related to damage caused by severe snow storms to properties located on the east coast, which is included in Casualty-related (recoveries)/charges, net on the Consolidated Statements of Operations.

Discontinued_Operations

Discontinued Operations	3 Months Ended
	Mar. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
DISCONTINUED OPERATIONS	DISCONTINUED OPERATIONS
	Effective January 1, 2014, UDR prospectively adopted ASU No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, for all communities not previously sold or classified as held for sale. The standard had a material impact on the Company’s consolidated financial statements. As a result of adopting the ASU, during the three months ended March 31, 2014, gains (net of tax) of $23.3 million from disposition of real estate, excluding a $1.1 million gain related to the sale of land, are included in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations rather than in Income/(loss) from discontinued operations, net of tax on the Consolidated Statements of Operations.
	As of March 31, 2014, the Company held one operating property that was classified as held for disposition prior to the adoption of ASU 2014-08 and, therefore, met the requirements to be reported as a discontinued operation. The operating results of the property for the three months ended March 31, 2014 are included in Income/(loss) from discontinued operations, net of tax on the Consolidated Statements of Operations. The property was subsequently sold during the third quarter of 2014.
	The following is a summary of income/(loss) from discontinued operations, net of tax for the three months ended March 31, 2015 and 2014 (dollars in thousands):


		Three Months Ended
		March 31,
		2015		2014
	Rental income	$	—	$	48

	Rental expenses	—		125

	Property management	—		1

	Interest and other (income)/expense, net	—		9

	Income/(loss) from discontinued operations, net of tax	$	—	$	(87	)


	Income/(loss) from discontinued operations attributable to UDR, Inc.	$	—	$	(84	)

Joint_Ventures

Joint Ventures	3 Months Ended
Joint Ventures	Mar. 31, 2015
Schedule of Equity Method Investments [Line Items]
Equity Method Investments and Joint Ventures Disclosure [Text Block]	JOINT VENTURES AND PARTNERSHIPS
	UDR has entered into joint ventures and partnerships with unrelated third parties to acquire real estate assets that are either consolidated and included in Real estate owned on the Consolidated Balance Sheets or are accounted for under the equity method of accounting, and are included in Investment in and advances to unconsolidated joint ventures, net on the Consolidated Balance Sheets. The Company consolidates the entities that we control as well as any variable interest entity where we are the primary beneficiary. In addition, the Company consolidates any joint venture or partnership in which we are the general partner or managing member and the third party does not have the ability to substantively participate in the decision-making process nor the ability to remove us as general partner or managing member without cause.

	UDR’s joint ventures and partnerships are funded with a combination of debt and equity. Our losses are limited to our investment and except as noted below, the Company does not guarantee any debt, capital payout or other obligations associated with our joint ventures and partnerships.
	Unconsolidated Joint Ventures and Partnerships
	The Company recognizes earnings or losses from our investments in unconsolidated joint ventures and partnerships consisting of our proportionate share of the net earnings or losses of the joint ventures and partnerships. In addition, we may earn fees for providing management services to the unconsolidated joint ventures and partnerships.
	The following table summarizes the Company’s investment in and advances to unconsolidated joint ventures and partnerships, net, which are accounted for under the equity method of accounting as of March 31, 2015 and December 31, 2014 (dollars in thousands):


	Joint Venture		Location of Properties	Number of Properties		Number of Apartment Homes	Investment at					UDR’s Ownership Interest
				March 31,		March 31,	March 31,		December 31,			March 31,			December 31,
				2015		2015	2015		2014			2015			2014
	Operating and development:
	UDR/MetLife I		Various	4 land parcels		—	$	13,473	$	13,306		15.7		%	15.7		%
	UDR/MetLife I		Various	4 land parcels		—	$	13,473	$	13,306		15.7		%	15.7		%
	UDR/MetLife II		Various	21 operating communities		4,642	429,635		431,277			50		%	50		%
	UDR/MetLife II		Various	21 operating communities		4,642	429,635		431,277			50		%	50		%
	Other UDR/MetLife Development Joint Ventures			1 operating community;
				4 development communities (a);
			Various	1 land parcels		1,437	145,681		134,939			50.6		%	50.6		%
			Various	1 land parcels		1,437	145,681		134,939			50.6		%	50.6		%
	UDR/MetLife Vitruvian Park®		Addison, TX	3 operating communities
				6 land parcels		1,130	78,669		80,302			50		%	50		%
				6 land parcels		1,130	78,669		80,302			50		%	50		%
	UDR/KFH		Washington, D.C.	3 operating communities		660	20,435		21,596			30		%	30		%
	UDR/KFH		Washington, D.C.	3 operating communities		660	20,435		21,596			30		%	30		%
	Texas (b)		Texas	—		—	—		(25,901		)	—		%	20		%
	Texas (b)		Texas	—		—	—		(25,901		)	—		%	20		%
	Investment in and advances to unconsolidated joint ventures, net, before participating loan investment						687,893		655,519
							687,893		655,519

			Location	Interest Rate		Years To Maturity	Investment at					Income From Participating Loan Investment for the Three Months Ended March 31,
							March 31,		December 31,			2015			2014
							2015		2014			2015			2014
	Participating loan investment:
	Steele Creek		Denver, CO	6.50%		2.3	75,647		62,707			$	1,154		$	321
	Steele Creek		Denver, CO	6.50%		2.3	75,647		62,707			$	1,154		$	321

	Total investment in and advances to unconsolidated joint ventures, net						$	763,540	$	718,226
							$	763,540	$	718,226

	(a)	The number of apartment homes for the communities under development presented in the table above is based on the projected number of total homes. As of March 31, 2015, no apartment homes had been completed in Other UDR/MetLife Development Joint Ventures.
	(b) In January 2015, the eight communities held by the Texas joint venture were sold, generating net proceeds to UDR of $43.5 million. The Company recorded promote and disposition fee income of $9.6 million and a gain of $59.1 million (including $24.2 million of previously deferred gains) in connection with the sale.
	Subsequent to quarter end, the Company entered into a joint venture agreement with real estate private equity firm, The Wolff Company (“Wolff”), to invest $136 million for a 48 percent interest in a portfolio of five communities that are currently under construction. The transaction is expected to close in May 2015. The communities are located in three of the Company’s core, coastal markets: Metro Seattle, Los Angeles and Orange County, CA. UDR will earn a 6.5 percent preferred return on its $136 million investment through each individual community’s date of stabilization, defined as when a community reaches 80 percent occupancy for ninety consecutive days, while Wolff is allocated all income and expense during the pre-stabilization period. Upon stabilization, income and expense will be shared based on each partner’s ownership percentage. The Company will serve as property manager and be paid a management fee during the lease-up phase and subsequent operation of each of the communities.

	The Company has a fixed price option to acquire Wolff’s remaining interest in each community beginning one year after completion. If the options are exercised for all five communities, the Company’s total price will be $597 million. In the event the Company does not exercise its options to purchase at least two communities, Wolff will be entitled to a 6.5 percent return on its implied equity in the communities not acquired. Wolff is providing certain guaranties and there will be construction loans on all five communities. Once completed the five communities will contain 1,533 homes.
	As of March 31, 2015 and December 31, 2014, the Company had deferred fees and deferred profit from the sale of properties to joint ventures or partnerships of $5.6 million and $28.5 million, respectively, which will be recognized through earnings over the weighted average life of the related properties, upon the disposition of the properties to a third party, or upon completion of certain development obligations.
	The Company recognized management fees for our management of the joint ventures and partnerships of $2.6 million and $3.3 million for the three months ended March 31, 2015 and 2014, respectively. The management fees are included in Joint venture management and other fees on the Consolidated Statements of Operations.
	The Company may, in the future, make additional capital contributions to certain of our joint ventures and partnerships should additional capital contributions be necessary to fund acquisitions or operations.
	We evaluate our investments in unconsolidated joint ventures and partnerships when events or changes in circumstances indicate that there may be an other-than-temporary decline in value. We consider various factors to determine if a decrease in the value of the investment is other-than-temporary. The Company did not recognize any other-than-temporary decreases in the value of its investments in unconsolidated joint ventures or partnerships during the three months ended March 31, 2015 and 2014.

	Combined summary balance sheets relating to all of the unconsolidated joint ventures and partnerships (not just our proportionate share) are presented below as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015			December 31, 2014
	Total real estate, net	$	2,970,102		$	2,941,803
	Total real estate, net	$	2,970,102		$	2,941,803
	Assets held for sale	—			216,196
	Assets held for sale	—			216,196
	Cash and cash equivalents	29,544			32,544
	Cash and cash equivalents	29,544			32,544
	Other assets	31,162			28,707
	Other assets	31,162			28,707
Total assets	$	3,030,808		$	3,219,250
Total assets	$	3,030,808		$	3,219,250

Amount due to UDR	$	4,691		$	2,997
Amount due to UDR	$	4,691		$	2,997
Third party debt	1,514,886			1,504,477
Third party debt	1,514,886			1,504,477
Liabilities held for sale	—			229,706
Liabilities held for sale	—			229,706
Accounts payable and accrued liabilities	52,146			44,335
Accounts payable and accrued liabilities	52,146			44,335
Total liabilities	1,571,723			1,781,515
Total liabilities	1,571,723			1,781,515
Total equity	1,459,085			1,437,735
Total equity	1,459,085			1,437,735
Total liabilities and equity	$	3,030,808		$	3,219,250
Total liabilities and equity	$	3,030,808		$	3,219,250

UDR’s investment in unconsolidated joint ventures	$	763,540		$	718,226
UDR’s investment in unconsolidated joint ventures	$	763,540		$	718,226
Combined summary financial information relating to all of the unconsolidated joint ventures’ and partnerships’ operations (not just our proportionate share), is presented below for the three months ended March 31, 2015 and 2014 (dollars in thousands):


	Three Months Ended
	March 31,
	2015			2014
Total revenues	$	54,546		$	38,955
Total revenues	$	54,546		$	38,955
Property operating expenses	(20,168		)	(14,360		)
Real estate depreciation and amortization	(19,351		)	(14,688		)
Operating income/(loss)	15,027			9,907
Operating income/(loss)	15,027			9,907
Interest expense	(16,061		)	(12,151		)
Income/(loss) from discontinued operations	182,488			(29,997		)
Income/(loss) from discontinued operations	182,488			(29,997		)
Net income/(loss)	$	181,454		$	(32,241	)
Net income/(loss)	$	181,454		$	(32,241	)
UDR income/(loss) from unconsolidated entities	$	59,159		$	(3,565	)
UDR income/(loss) from unconsolidated entities	$	59,159		$	(3,565	)

Secured_and_Unsecured_Debt

Secured and Unsecured Debt	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	SECURED AND UNSECURED DEBT
	The following is a summary of our secured and unsecured debt at March 31, 2015 and December 31, 2014 (dollars in thousands):


							Three Months Ended
		Principal Outstanding					31-Mar-15
		March 31,			December 31, 2014		Weighted Average		Weighted Average			Number of Communities
		2015					Interest Rate		Years to Maturity			Encumbered
	Secured Debt:
	Fixed Rate Debt
	Mortgage notes payable (a)	$	411,271		$	401,210	5.49	%	1.4			7

	Fannie Mae credit facilities (b)	567,169			568,086		5.12	%	3.8			22

	Total fixed rate secured debt	978,440			969,296		5.28	%	2.8			29

	Variable Rate Debt

	Mortgage notes payable	31,337			31,337		1.94	%	1.8			1

	Tax-exempt secured notes payable (c)	94,700			94,700		0.76	%	7.9			2

	Fannie Mae credit facilities (b)	266,196			266,196		1.62	%	4.9			7

	Total variable rate secured debt	392,233			392,233		1.44	%	5.4			10

	Total Secured Debt	1,370,673			1,361,529		4.18	%	3.5			39


	Unsecured Debt:
	Commercial Banks
	Borrowings outstanding under an unsecured credit facility due December 2017 (d) (f)	389,000			152,500		1.08	%	2.7

	Senior Unsecured Notes
	5.25% Medium-Term Notes due January 2015 (net of discounts of $0 and $6, respectively) (e)	—			325,169		—	%	—

	5.25% Medium-Term Notes due January 2016	83,260			83,260		5.25	%	0.8

	6.21% Medium-Term Notes due July 2016	12,865			—		6.21	%	1.3

	4.25% Medium-Term Notes due June 2018 (net of discounts of $1,358 and $1,465, respectively) (f)	298,642			298,535		4.25	%	3.2

	1.70% Term Notes due June 2018 (f)	215,000			215,000		1.7	%	3.2

	1.53% Term Notes due June 2018 (f)	100,000			100,000		1.53	%	3.2

	1.32% Term Notes due June 2018 (f)	35,000			35,000		1.32	%	3.2

	3.70% Medium-Term Notes due October 2020 (net of discounts of $44 and $46, respectively) (f)	299,956			299,954		3.7	%	5.5

	4.63% Medium-Term Notes due January 2022 (net of discounts of $2,433 and $2,523, respectively) (f)	397,567			397,477		4.63	%	6.8

	3.75% Medium-Term Notes due July 2024 (net of discount of $964 and $990, respectively) (f)	299,036			299,010		3.75	%	9.3

	8.50% Debentures due September 2024	15,644			15,644		8.5	%	9.5

	Other	26			27		N/A		N/A

	Total Unsecured Debt	2,145,996			2,221,576		3.26	%	4.9

	Total Debt	$	3,516,669		$	3,583,105	3.62	%	4.4


	Our secured debt instruments generally feature either monthly interest and principal or monthly interest-only payments with balloon payments due at maturity. For purposes of classification of the above table, variable rate debt with a derivative financial instrument designated as a cash flow hedge is deemed as fixed rate debt due to the Company having effectively established a fixed interest rate for the underlying debt instrument. Secured debt encumbers $2.3 billion or 26.7% of UDR’s total real estate owned based upon gross book value ($6.2 billion or 73.3% of UDR’s real estate owned based on gross book value is unencumbered) as of March 31, 2015.
(a) At March 31, 2015, fixed rate mortgage notes payable are generally due in monthly installments of principal and interest and mature at various dates from December 2015 through May 2019 and carry interest rates ranging from 3.43% to 6.16%.
The Company will from time to time acquire properties subject to fixed rate debt instruments. In those situations, the Company records the debt at its estimated fair value and amortizes any difference between the fair value and par to interest expense over the life of the underlying debt instrument. The Company had a reduction to interest expense based on the amortization of the fair market adjustment of debt assumed in the acquisition of properties of $1.1 million and $1.3 million during the three months ended March 31, 2015 and 2014, respectively. The unamortized fair market adjustment was a net premium of $7.0 million and $6.7 million at March 31, 2015 and December 31, 2014, respectively.
(b) UDR has three secured credit facilities with Fannie Mae with an aggregate commitment of $833.4 million at March 31, 2015. The Fannie Mae credit facilities mature at various dates from May 2017 through July 2023 and bear interest at floating and fixed rates. At March 31, 2015, $567.2 million of the outstanding balance was fixed and had a weighted average interest rate of 5.12% and the remaining balance of $266.2 million had a weighted average variable interest rate of 1.62%.
Further information related to these credit facilities is as follows (dollars in thousands):


	March 31,			December 31, 2014
	2015
Borrowings outstanding	$	833,365		$	834,282

Weighted average borrowings during the period ended	833,697			835,873

Maximum daily borrowings during the period ended	834,003			837,564

Weighted average interest rate during the period ended	4		%	4.1		%
Weighted average interest rate at the end of the period	4		%	4		%
(c) The variable rate mortgage notes payable that secure tax-exempt housing bond issues mature in August 2019 and March 2032. Interest on these notes is payable in monthly installments. The variable rate mortgage notes have interest rates of 0.76% and 0.77% as of March 31, 2015.

(d) As of March 31, 2015, the Company has a $900 million unsecured revolving credit facility that matures in December 2017. The credit facility has a six month extension option and contains an accordion feature that allows us to increase the facility to $1.45 billion. Based on the Company’s current credit rating, the credit facility carries an interest rate equal to LIBOR plus a spread of 100 basis points and a facility fee of 15 basis points.

The following is a summary of short-term bank borrowings under UDR’s revolving credit facility at March 31, 2015 and December 31, 2014 (dollars in thousands):


	March 31,			December 31, 2014
	2015
Total revolving credit facility	$	900,000		$	900,000

Borrowings outstanding at end of period (1)	389,000			152,500

Weighted average daily borrowings during the period ended	356,043			291,761

Maximum daily borrowings during the period ended	449,500			625,000

Weighted average interest rate during the period ended	1.2		%	1.2		%
Interest rate at end of the period	1.1		%	1.1		%
(1) Excludes $1.5 million and $1.9 million of letters of credit at March 31, 2015 and December 31, 2014, respectively.

(e) Paid off at maturity with borrowings under the Company's $900 million unsecured revolving credit facility.

(f) The Operating Partnership is a guarantor of this debt.

The aggregate maturities, including amortizing principal payments of unsecured and secured debt, of total debt for the next five calendar years subsequent to March 31, 2015 are as follows (dollars in thousands):


Year		Total Fixed Secured Debt			Total Variable Secured Debt		Total Secured Debt			Total Unsecured Debt (a)			Total Debt
2015		$	194,779		$	—	$	194,779		$	114		$	194,893

2016		148,223			—		148,223			94,468			242,691

2017		177,882			96,337		274,219			389,000			663,219

2018		121,685			104,787		226,472			648,444			874,916

2019		245,871			67,700		313,571			—			313,571

Thereafter		90,000			123,409		213,409			1,013,970			1,227,379

Total		$	978,440		$	392,233	$	1,370,673		$	2,145,996		$	3,516,669

(a) With the exception of the 1.32% Term Notes due June 2018 and the revolving credit facility which carry a variable interest rate, all unsecured debt carries fixed interest rates.
We were in compliance with the covenants of our debt instruments at March 31, 2015.

Debt_UNITED_DOMINION_REALTY_LP

Debt (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
DEBT	SECURED AND UNSECURED DEBT
	The following is a summary of our secured and unsecured debt at March 31, 2015 and December 31, 2014 (dollars in thousands):


									Three Months Ended
		Principal Outstanding							31-Mar-15
		March 31,				December 31, 2014			Weighted Average			Weighted Average			Number of Communities
		2015							Interest Rate			Years to Maturity			Encumbered
	Secured Debt:
	Fixed Rate Debt
	Mortgage notes payable (a)	$	411,271			$	401,210		5.49	%		1.4			7

	Fannie Mae credit facilities (b)	567,169				568,086			5.12	%		3.8			22

	Total fixed rate secured debt	978,440				969,296			5.28	%		2.8			29

	Variable Rate Debt

	Mortgage notes payable	31,337				31,337			1.94	%		1.8			1

	Tax-exempt secured notes payable (c)	94,700				94,700			0.76	%		7.9			2

	Fannie Mae credit facilities (b)	266,196				266,196			1.62	%		4.9			7

	Total variable rate secured debt	392,233				392,233			1.44	%		5.4			10

	Total Secured Debt	1,370,673				1,361,529			4.18	%		3.5			39


	Unsecured Debt:
	Commercial Banks
	Borrowings outstanding under an unsecured credit facility due December 2017 (d) (f)	389,000				152,500			1.08	%		2.7

	Senior Unsecured Notes
	5.25% Medium-Term Notes due January 2015 (net of discounts of $0 and $6, respectively) (e)	—				325,169			—	%		—

	5.25% Medium-Term Notes due January 2016	83,260				83,260			5.25	%		0.8

	6.21% Medium-Term Notes due July 2016	12,865				—			6.21	%		1.3

	4.25% Medium-Term Notes due June 2018 (net of discounts of $1,358 and $1,465, respectively) (f)	298,642				298,535			4.25	%		3.2

	1.70% Term Notes due June 2018 (f)	215,000				215,000			1.7	%		3.2

	1.53% Term Notes due June 2018 (f)	100,000				100,000			1.53	%		3.2

	1.32% Term Notes due June 2018 (f)	35,000				35,000			1.32	%		3.2

	3.70% Medium-Term Notes due October 2020 (net of discounts of $44 and $46, respectively) (f)	299,956				299,954			3.7	%		5.5

	4.63% Medium-Term Notes due January 2022 (net of discounts of $2,433 and $2,523, respectively) (f)	397,567				397,477			4.63	%		6.8

	3.75% Medium-Term Notes due July 2024 (net of discount of $964 and $990, respectively) (f)	299,036				299,010			3.75	%		9.3

	8.50% Debentures due September 2024	15,644				15,644			8.5	%		9.5

	Other	26				27			N/A			N/A

	Total Unsecured Debt	2,145,996				2,221,576			3.26	%		4.9

	Total Debt	$	3,516,669			$	3,583,105		3.62	%		4.4


	Our secured debt instruments generally feature either monthly interest and principal or monthly interest-only payments with balloon payments due at maturity. For purposes of classification of the above table, variable rate debt with a derivative financial instrument designated as a cash flow hedge is deemed as fixed rate debt due to the Company having effectively established a fixed interest rate for the underlying debt instrument. Secured debt encumbers $2.3 billion or 26.7% of UDR’s total real estate owned based upon gross book value ($6.2 billion or 73.3% of UDR’s real estate owned based on gross book value is unencumbered) as of March 31, 2015.
(a) At March 31, 2015, fixed rate mortgage notes payable are generally due in monthly installments of principal and interest and mature at various dates from December 2015 through May 2019 and carry interest rates ranging from 3.43% to 6.16%.
The Company will from time to time acquire properties subject to fixed rate debt instruments. In those situations, the Company records the debt at its estimated fair value and amortizes any difference between the fair value and par to interest expense over the life of the underlying debt instrument. The Company had a reduction to interest expense based on the amortization of the fair market adjustment of debt assumed in the acquisition of properties of $1.1 million and $1.3 million during the three months ended March 31, 2015 and 2014, respectively. The unamortized fair market adjustment was a net premium of $7.0 million and $6.7 million at March 31, 2015 and December 31, 2014, respectively.
(b) UDR has three secured credit facilities with Fannie Mae with an aggregate commitment of $833.4 million at March 31, 2015. The Fannie Mae credit facilities mature at various dates from May 2017 through July 2023 and bear interest at floating and fixed rates. At March 31, 2015, $567.2 million of the outstanding balance was fixed and had a weighted average interest rate of 5.12% and the remaining balance of $266.2 million had a weighted average variable interest rate of 1.62%.
Further information related to these credit facilities is as follows (dollars in thousands):


	March 31,				December 31, 2014
	2015
Borrowings outstanding	$	833,365			$	834,282

Weighted average borrowings during the period ended	833,697				835,873

Maximum daily borrowings during the period ended	834,003				837,564

Weighted average interest rate during the period ended	4		%		4.1		%
Weighted average interest rate at the end of the period	4		%		4		%
(c) The variable rate mortgage notes payable that secure tax-exempt housing bond issues mature in August 2019 and March 2032. Interest on these notes is payable in monthly installments. The variable rate mortgage notes have interest rates of 0.76% and 0.77% as of March 31, 2015.

(d) As of March 31, 2015, the Company has a $900 million unsecured revolving credit facility that matures in December 2017. The credit facility has a six month extension option and contains an accordion feature that allows us to increase the facility to $1.45 billion. Based on the Company’s current credit rating, the credit facility carries an interest rate equal to LIBOR plus a spread of 100 basis points and a facility fee of 15 basis points.

The following is a summary of short-term bank borrowings under UDR’s revolving credit facility at March 31, 2015 and December 31, 2014 (dollars in thousands):


	March 31,				December 31, 2014
	2015
Total revolving credit facility	$	900,000			$	900,000

Borrowings outstanding at end of period (1)	389,000				152,500

Weighted average daily borrowings during the period ended	356,043				291,761

Maximum daily borrowings during the period ended	449,500				625,000

Weighted average interest rate during the period ended	1.2		%		1.2		%
Interest rate at end of the period	1.1		%		1.1		%
(1) Excludes $1.5 million and $1.9 million of letters of credit at March 31, 2015 and December 31, 2014, respectively.

(e) Paid off at maturity with borrowings under the Company's $900 million unsecured revolving credit facility.

(f) The Operating Partnership is a guarantor of this debt.

The aggregate maturities, including amortizing principal payments of unsecured and secured debt, of total debt for the next five calendar years subsequent to March 31, 2015 are as follows (dollars in thousands):


Year		Total Fixed Secured Debt				Total Variable Secured Debt			Total Secured Debt				Total Unsecured Debt (a)			Total Debt
2015		$	194,779			$	—		$	194,779			$	114		$	194,893

2016		148,223				—			148,223				94,468			242,691

2017		177,882				96,337			274,219				389,000			663,219

2018		121,685				104,787			226,472				648,444			874,916

2019		245,871				67,700			313,571				—			313,571

Thereafter		90,000				123,409			213,409				1,013,970			1,227,379

Total		$	978,440			$	392,233		$	1,370,673			$	2,145,996		$	3,516,669

(a) With the exception of the 1.32% Term Notes due June 2018 and the revolving credit facility which carry a variable interest rate, all unsecured debt carries fixed interest rates.
We were in compliance with the covenants of our debt instruments at March 31, 2015.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
DEBT	DEBT
	Our secured debt instruments generally feature either monthly interest and principal or monthly interest-only payments with balloon payments due at maturity. For purposes of classification in the following table, variable rate debt with a derivative financial instrument designated as a cash flow hedge is deemed as fixed rate debt due to the Operating Partnership having effectively established the fixed interest rate for the underlying debt instrument. Secured debt consists of the following as of March 31, 2015 and December 31, 2014 (dollars in thousands):


									Three Months Ended
		Principal Outstanding							31-Mar-15
		March 31,				December 31, 2014			Weighted Average			Weighted Average		Number of Communities
		2015							Interest Rate			Years to Maturity		Encumbered
	Fixed Rate Debt
	Mortgage notes payable	$	376,207			$	378,371		5.48	%		1.4		5

	Fannie Mae credit facilities	333,735				333,828			4.9	%		4.3		10

	Total fixed rate secured debt	709,942				712,199			5.21	%		2.8		15

	Variable Rate Debt
	Tax-exempt secured note payable	27,000				27,000			0.77	%		17		1

	Fannie Mae credit facilities	192,760				192,760			1.85	%		5.7		5

	Total variable rate secured debt	219,760				219,760			1.72	%		7.1		6

	Total Secured Debt	$	929,702			$	931,959		4.38	%		3.8		21

	As of March 31, 2015, an aggregate commitment of $526.5 million of the General Partner's secured credit facilities with Fannie Mae was allocated to the Operating Partnership based on the ownership of the assets securing the debt. The entire commitment was outstanding at March 31, 2015. The Fannie Mae credit facilities mature at various dates from May 2017 through July 2023 and bear interest at floating and fixed rates. At March 31, 2015, $333.7 million of the outstanding balance was fixed and had a weighted average interest rate of 4.90% and the remaining balance of $192.8 million on these facilities had a weighted average variable interest rate of 1.85%.
	The following information relates to the credit facilities allocated to the Operating Partnership (dollars in thousands):


		March 31,				December 31, 2014
		2015
	Borrowings outstanding	$	526,495			$	526,588

	Weighted average borrowings during the period ended	526,705				527,592

	Maximum daily borrowings during the period	526,898				528,659

	Weighted average interest rate during the period ended	4		%		4.1		%
	Interest rate at the end of the period	4		%		4		%
	The Operating Partnership may from time to time acquire properties subject to fixed rate debt instruments. In those situations, management will record the secured debt at its estimated fair value and amortize any difference between the fair value and par to interest expense over the life of the underlying debt instrument. The unamortized fair value adjustment of the fixed rate debt instruments on the Operating Partnership’s properties was a net premium of $5.2 million and $6.2 million at March 31, 2015 and December 31, 2014, respectively.
	Fixed Rate Debt
	Mortgage notes payable. Fixed rate mortgage notes payable are generally due in monthly installments of principal and interest and mature at various dates from December 2015 through May 2019 and carry interest rates ranging from 3.43% to 5.94%.
	Secured credit facilities. At March 31, 2015, the General Partner had borrowings against its fixed rate facilities of $567.2 million, of which $333.7 million was allocated to the Operating Partnership based on the ownership of the assets securing the debt. As of March 31, 2015, the fixed rate Fannie Mae credit facilities allocated to the Operating Partnership had a weighted average fixed interest rate of 4.90%.
	Variable Rate Debt
	Tax-exempt secured note payable. The variable rate mortgage note payable that secures tax-exempt housing bond issues matures March 2032. Interest on this note is payable in monthly installments. The mortgage note payable has an interest rate of 0.77% as of March 31, 2015.
	Secured credit facilities. At March 31, 2015, the General Partner had borrowings against its variable rate facilities of $266.2 million, of which $192.8 million was allocated to the Operating Partnership based on the ownership of the assets securing the debt. As of March 31, 2015, the variable rate borrowings under the Fannie Mae credit facilities allocated to the Operating Partnership had a weighted average floating interest rate of 1.85%.
	The aggregate maturities of the Operating Partnership’s secured debt due during each of the next five calendar years subsequent to March 31, 2015 are as follows (dollars in thousands):


			Fixed							Variable
	Year		Mortgage				Secured Credit			Tax-Exempt				Secured Credit			Total
			Notes Payable				Facilities			Secured Notes Payable				Facilities
	2015		$	190,582			$	274		$	—			$	—		$	190,856

	2016		131,021				385			—				—			131,406

	2017		913				15,640			—				6,566			23,119

	2018		968				111,052			—				96,974			208,994

	2019		52,723				123,095			—				—			175,818

	Thereafter		—				83,289			27,000				89,220			199,509

	Total		$	376,207			$	333,735		$	27,000			$	192,760		$	929,702

Guarantor on Unsecured Debt
The Operating Partnership is a guarantor on the General Partner’s unsecured revolving credit facility with an aggregate borrowing capacity of $900 million, $250 million of term notes due June 2018, $100 million of term notes due June 2018, $300 million of medium-term notes due June 2018, $300 million of medium-term notes due October 2020, $400 million of medium-term notes due January 2022, and $300 million of medium-term notes due July 2024. As of March 31, 2015 and December 31, 2014, the outstanding balance under the unsecured revolving credit facility was $389.0 million and $152.5 million, respectively.

IncomeLoss_Per_Share

Income/(Loss) Per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
EARNINGS/(LOSS) PER SHARE	/(LOSS) PER SHARE
	The following table sets forth the computation of basic and diluted income/(loss) per share for the periods presented (dollars and shares in thousands, except per share data):


		Three Months Ended
		March 31,
		2015				2014
	Numerator for income/(loss) per share:
	Income/(loss) from continuing operations	$	76,417			$	(5,195	)

	Gain/(loss) on sale of real estate owned, net of tax	—				24,294

	(Income)/loss from continuing operations attributable to redeemable noncontrolling interests in the Operating Partnership	(2,588		)		(650		)
	(Income)/loss from continuing operations attributable to noncontrolling interests	(7		)		(4		)
	Income/(loss) from continuing operations attributable to UDR, Inc.	73,822				18,445

	Distributions to preferred stockholders - Series E (Convertible)	(931		)		(931		)
	Income/(loss) from continuing operations attributable to common stockholders	$	72,891			$	17,514


	Income/(loss) from discontinued operations, net of tax	$	—			$	(87	)

	(Income)/loss from discontinued operations attributable to redeemable noncontrolling interests in the Operating Partnership	—				3

	Income/(loss) from discontinued operations attributable to common stockholders	$	—			$	(84	)


	Net income/(loss) attributable to common stockholders	$	72,891			$	17,430


	Denominator for income/(loss) per share:
	Weighted average common shares outstanding	258,100				251,213

	Non-vested restricted stock awards	(1,266		)		(1,036		)
	Denominator for basic income/(loss) per share	256,834				250,177

	Incremental shares issuable from assumed conversion of stock options and unvested restricted stock	1,828				1,645

	Denominator for diluted income/(loss) per share	258,662				251,822


	Income/(loss) per weighted average common share-basic:
	Income/(loss) from continuing operations attributable to common stockholders	$	0.28			$	0.07

	Income/(loss) from discontinued operations attributable to common stockholders	0				0

	Net income/(loss) attributable to common stockholders	$	0.28			$	0.07


	Income/(loss) per weighted average common share-diluted:
	Income/(loss) from continuing operations attributable to common stockholders	$	0.28			$	0.07

	Income/(loss) from discontinued operations attributable to common stockholders	0				0

	Net income/(loss) attributable to common stockholders	$	0.28			$	0.07

	Basic income/(loss) per common share is computed based upon the weighted average number of common shares outstanding. Diluted income/(loss) per share is computed based upon the weighted average number of common shares outstanding plus the common shares issuable from the assumed conversion of the OP Units, convertible preferred stock, stock options, and restricted stock. Only those instruments having a dilutive impact on our basic income/(loss) per share are included in diluted income/(loss) per share during the periods.

	The following table sets forth the additional shares of common stock outstanding by equity instrument if converted to common stock for each of the three months ended March 31, 2015 and 2014 (shares in thousands):


		Three Months Ended
		March 31,
		2015			2014
OP Units	9,165			9,319

Preferred stock	3,036			3,036

Stock options and unvested restricted stock	1,828			1,645

Noncontrolling_Interests

Noncontrolling Interests	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest [Abstract]
NONCONTROLLING INTERESTS	NONCONTROLLING INTERESTS
	Redeemable Noncontrolling Interests in the Operating Partnership
	Interests in the Operating Partnership held by limited partners are represented by OP Units. The income is allocated to holders of OP Units based upon net income attributable to common stockholders and the weighted average number of OP Units outstanding to total common shares plus OP Units outstanding during the period. Capital contributions, distributions, and profits and losses are allocated to noncontrolling interests in accordance with the terms of the individual partnership agreements.
	Limited partners have the right to require the Operating Partnership to redeem all or a portion of the OP Units held by the limited partners at a redemption price equal to and in the form of the Cash Amount as defined in the Amended and Restated Agreement of Limited Partnership of the Operating Partnership (the “Operating Partnership Agreement”), provided that such OP Units have been outstanding for at least one year. UDR, as the general partner of the Operating Partnership may, in its sole discretion, purchase the OP Units by paying to the limited partner either the Cash Amount or the REIT Share Amount (generally one share of common stock of the Company for each OP Unit), as defined in the Operating Partnership Agreement. Accordingly, the Company records the OP Units outside of permanent equity and reports the OP Units at their redemption value using the Company’s stock price at each balance sheet date.
	The following table sets forth redeemable noncontrolling interests in the Operating Partnership for the following period (dollars in thousands):


	Redeemable noncontrolling interests in the Operating Partnership, December 31, 2014	$	282,480

	Mark-to-market adjustment to redeemable noncontrolling interests in the Operating Partnership	29,696

	Conversion of OP Units to Common Stock	(17		)
	Net income/(loss) attributable to redeemable noncontrolling interests in the Operating Partnership	2,588

	Distributions to redeemable noncontrolling interests in the Operating Partnership	(2,639		)
	Allocation of other comprehensive income/(loss)	(225		)
	Redeemable noncontrolling interests in the Operating Partnership, March 31, 2015	$	311,883


	The following sets forth net income/(loss) attributable to common stockholders and transfers from redeemable noncontrolling interests in the Operating Partnership for the following periods (dollars in thousands):


		Three Months Ended
		March 31,
		2015			2014
	Net income/(loss) attributable to common stockholders	$	72,891		$	17,430

	Conversion of OP Units to UDR Common stock	17			—

	Change in equity from net income/(loss) attributable to common stockholders and conversion of OP Units to UDR Common Stock	$	72,908		$	17,430

	Noncontrolling Interests
	Noncontrolling interests represent interests of unrelated partners in certain consolidated affiliates, and are presented as part of equity in the Consolidated Balance Sheets since these interests are not redeemable. Net (income)/loss attributable to noncontrolling interests was $(7,000) and $(4,000) during the three months ended March 31, 2015 and 2014, respectively

Related_Party_Transactions_UNI

Related Party Transactions (UNITED DOMINION REALTY, L.P.) (United Dominion Reality L.P. [Member])	3 Months Ended
	Mar. 31, 2015
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS
	Advances (To)/From the General Partner
	The Operating Partnership participates in the General Partner’s central cash management program, wherein all the Operating Partnership’s cash receipts are remitted to the General Partner and all cash disbursements are funded by the General Partner. In addition, other miscellaneous costs such as administrative expenses are incurred by the General Partner on behalf of the Operating Partnership. As a result of these various transactions between the Operating Partnership and the General Partner, the Operating Partnership had net Advances (to)/from General Partner of $22.4 million and $13.6 million at March 31, 2015 and December 31, 2014, respectively, which are reflected as increases of capital on the Consolidated Balance Sheets.
	Allocation of General and Administrative Expenses
	The General Partner provides various general and administrative and other overhead services for the Operating Partnership including legal assistance, acquisitions analysis, marketing and advertising, and allocates these expenses to the Operating Partnership first on the basis of direct usage when identifiable, with the remainder allocated based on its pro-rata portion of UDR’s total apartment homes. The general and administrative expenses allocated to the Operating Partnership by UDR were $4.2 million and $6.7 million during the three months ended March 31, 2015 and 2014, respectively, and are included in General and administrative on the Consolidated Statements of Operations. In the opinion of management, this method of allocation reflects the level of services received by the Operating Partnership from the General Partner.
	During the three months ended March 31, 2015 and 2014, the Operating Partnership incurred $4.3 million and $3.1 million, respectively, of related party management fees related to a management agreement entered into in 2011 with wholly-owned subsidiaries of UDR's taxable REIT subsidiary ("TRS"). (See further discussion in paragraph below.) These related party management fees are initially recorded in General and administrative on the Consolidated Statements of Operations, and a portion related to management fees charged by UDR's TRS is reclassified to Property management on the Consolidated Statements of Operations. (See further discussion below.)
	Management Fee
	In 2011, the Operating Partnership entered into a management agreement with wholly owned subsidiaries of UDR's TRS. Under the management agreement, the Operating Partnership is charged a management fee equal to 2.75% of gross rental revenues, which is classified in Property management on the Consolidated Statements of Operations.
	Notes Payable to General Partner
	As of March 31, 2015 and December 31, 2014, the Operating Partnership had $88.7 million of unsecured notes payable to the General Partner at annual interest rates between 5.18% and 5.34%. Certain limited partners of the Operating Partnership have provided guarantees related to these notes payable. The guarantees were provided by the limited partners in conjunction with their contribution of properties to the Operating Partnership. The notes mature on August 31, 2021 and December 31, 2023 and interest payments are made monthly. The Operating Partnership recognized interest expense on the notes payable of $1.2 million and $1.2 million during the three months ended March 31, 2015 and 2014, respectively.

Fair_Value_of_Derivatives_and_

Fair Value of Derivatives and Financial Instruments	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS	FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS
	Fair value is based on the price that would be received to sell an asset or the exit price that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three-level valuation hierarchy prioritizes observable and unobservable inputs used to measure fair value. The fair value hierarchy consists of three broad levels, which are described below:

	•	Level 1 — Quoted prices in active markets for identical assets or liabilities that the entity has the ability to access.

	•	Level 2 — Observable inputs other than prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated with observable market data.

	•	Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
	The estimated fair values of the Company’s financial instruments either recorded or disclosed on a recurring basis as of March 31, 2015 and December 31, 2014 are summarized as follows (dollars in thousands):


								Fair Value at March 31, 2015, Using
		Total Carrying Amount in Statement of Financial Position at March 31, 2015			Fair Value Estimate at March 31, 2015			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	15,494		$	15,923		$	—		$	—		$	15,923

	Derivatives - Interest rate contracts (b)	29			29			—			29			—

	Total assets	$	15,523		$	15,952		$	—		$	29		$	15,923


	Derivatives - Interest rate contracts (b)	$	17,112		$	17,112		$	—		$	17,112		$	—

	Secured debt instruments - fixed rate: (c)
	Mortgage notes payable	411,271			425,969			—			—			425,969

	Fannie Mae credit facilities	567,169			599,580			—			—			599,580

	Secured debt instruments - variable rate: (c)
	Mortgage notes payable	31,337			31,337			—			—			31,337

	Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

	Fannie Mae credit facilities	266,196			266,196			—			—			266,196

	Unsecured debt instruments: (c)
	Commercial bank	389,000			389,000			—			—			389,000

	Senior unsecured notes	1,756,996			1,852,361			—			—			1,852,361

	Total liabilities	$	3,533,781		$	3,676,255		$	—		$	17,112		$	3,659,143


	Redeemable noncontrolling interests in the Operating Partnership (d)	$	311,883		$	311,883		$	—		$	311,883		$	—



								Fair Value at December 31, 2014, Using
		Total Carrying Amount in Statement of Financial Position at December 31, 2014			Fair Value Estimate at December 31, 2014			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	14,369		$	14,808		$	—		$	—		$	14,808

	Derivatives- Interest rate contracts (b)	88			88			—			88			—

Total assets	$	14,457		$	14,896		$	—		$	88		$	14,808


Derivatives- Interest rate contracts (b)	$	10,368		$	10,368		$	—		$	10,368		$	—

Secured debt instruments- fixed rate: (c)
Mortgage notes payable	401,210			415,663			—			—			415,663

Fannie Mae credit facilities	568,086			606,623			—			—			606,623

Secured debt instruments- variable rate: (c)

Mortgage notes payable	31,337			31,337			—			—			31,337

Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

Fannie Mae credit facilities	266,196			266,196			—			—			266,196

Unsecured debt instruments: (c)
Commercial bank	152,500			152,500			—			—			152,500

Senior unsecured notes	2,069,076			2,144,125			—			—			2,144,125

Total liabilities	$	3,593,473		$	3,721,512		$	—		$	10,368		$	3,711,144


Redeemable noncontrolling interests in the Operating Partnership (d)	$	282,480		$	282,480		$	—		$	282,480		$	—



(a)	See Note 2, Significant Accounting Policies.

(b)	See Note 10, Derivatives and Hedging Activity.

(c)	See Note 6, Secured and Unsecured Debt.

(d)	See Note 8, Noncontrolling Interests.

There were no transfers into or out of each of the levels of the fair value hierarchy.
Financial Instruments Carried at Fair Value
The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. The fair values of interest rate options are determined using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates rise above the strike rate of the caps. The variable interest rates used in the calculation of projected receipts on the cap are based on an expectation of future interest rates derived from observable market interest rate curves and volatilities.
The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees.
Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. However, as of March 31, 2015 and December 31, 2014, the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. In conjunction with the FASB’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio.
Redeemable noncontrolling interests in the Operating Partnership have a redemption feature and are marked to their redemption value. The redemption value is based on the fair value of the Company’s common stock at the redemption date, and therefore, is calculated based on the fair value of the Company’s common stock at the balance sheet date. Since the valuation is based on observable inputs such as quoted prices for similar instruments in active markets, redeemable noncontrolling interests in the Operating Partnership are classified as Level 2.
Financial Instruments Not Carried at Fair Value
At March 31, 2015, the fair values of cash and cash equivalents, restricted cash, accounts receivable, prepaids, real estate taxes payable, accrued interest payable, security deposits and prepaid rent, distributions payable and accounts payable approximated their carrying values because of the short term nature of these instruments. The estimated fair values of other financial instruments were determined by the Company using available market information and appropriate valuation methodologies. Considerable judgment is necessary to interpret market data and develop estimated fair values. Accordingly, the estimates presented herein are not necessarily indicative of the amounts the Company would realize on the disposition of the financial instruments. The use of different market assumptions or estimation methodologies may have a material effect on the estimated fair value amounts.
We estimate the fair value of our notes receivable and debt instruments by discounting the remaining cash flows of the debt instrument at a discount rate equal to the replacement market credit spread plus the corresponding treasury yields. Factors considered in determining a replacement market credit spread include general market conditions, borrower specific credit spreads, time remaining to maturity, loan-to-value ratios and collateral quality, where applicable (Level 3).
We record impairment losses on long-lived assets used in operations when events and circumstances indicate that the assets might be impaired and the undiscounted cash flows estimated to be generated by the future operation and disposition of those assets are less than the net book value of those assets. Our cash flow estimates are based upon historical results adjusted to reflect our best estimate of future market and operating conditions and our estimated holding periods. The net book value of impaired assets is reduced to fair value. Our estimates of fair value represent our best estimate based upon Level 3 inputs such as industry trends and reference to market rates and transactions.
We consider various factors to determine if a decrease in the value of our investment in and advances to unconsolidated joint ventures, net is other-than-temporary. These factors include, but are not limited to, age of the venture, our intent and ability to retain our investment in the entity, the financial condition and long-term prospects of the entity, and the relationships with the other joint venture partners and its lenders. Based on the significance of the unobservable inputs, we classify these fair value measurements within Level 3 of the valuation hierarchy. The Company did not incur any other-than-temporary decrease in the value of its investments in unconsolidated joint ventures during the three months ended March 31, 2015 and 2014.
After determining an other-than-temporary decrease in the value of an equity method investment has occurred, we estimate the fair value of our investment by estimating the proceeds we would receive upon a hypothetical liquidation of the investment at the date of measurement. Inputs reflect management’s best estimate of what market participants would use in pricing the investment giving consideration to the terms of the joint venture agreement and the estimated discounted future cash flows to be generated from the underlying joint venture assets. The inputs and assumptions utilized to estimate the future cash flows of the underlying assets are based upon the Company’s evaluation of the economy, market trends, operating results, and other factors, including judgments regarding costs to complete any construction activities, lease up and occupancy rates, rental rates, inflation rates, capitalization rates utilized to estimate the projected cash flows at the disposition, and discount rates.

Fair_Value_of_Derivatives_and_1

Fair Value of Derivatives and Financial Instruments (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS	FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS
	Fair value is based on the price that would be received to sell an asset or the exit price that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three-level valuation hierarchy prioritizes observable and unobservable inputs used to measure fair value. The fair value hierarchy consists of three broad levels, which are described below:

	•	Level 1 — Quoted prices in active markets for identical assets or liabilities that the entity has the ability to access.

	•	Level 2 — Observable inputs other than prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated with observable market data.

	•	Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
	The estimated fair values of the Company’s financial instruments either recorded or disclosed on a recurring basis as of March 31, 2015 and December 31, 2014 are summarized as follows (dollars in thousands):


								Fair Value at March 31, 2015, Using
		Total Carrying Amount in Statement of Financial Position at March 31, 2015			Fair Value Estimate at March 31, 2015			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	15,494		$	15,923		$	—		$	—		$	15,923

	Derivatives - Interest rate contracts (b)	29			29			—			29			—

	Total assets	$	15,523		$	15,952		$	—		$	29		$	15,923


	Derivatives - Interest rate contracts (b)	$	17,112		$	17,112		$	—		$	17,112		$	—

	Secured debt instruments - fixed rate: (c)
	Mortgage notes payable	411,271			425,969			—			—			425,969

	Fannie Mae credit facilities	567,169			599,580			—			—			599,580

	Secured debt instruments - variable rate: (c)
	Mortgage notes payable	31,337			31,337			—			—			31,337

	Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

	Fannie Mae credit facilities	266,196			266,196			—			—			266,196

	Unsecured debt instruments: (c)
	Commercial bank	389,000			389,000			—			—			389,000

	Senior unsecured notes	1,756,996			1,852,361			—			—			1,852,361

	Total liabilities	$	3,533,781		$	3,676,255		$	—		$	17,112		$	3,659,143


	Redeemable noncontrolling interests in the Operating Partnership (d)	$	311,883		$	311,883		$	—		$	311,883		$	—



								Fair Value at December 31, 2014, Using
		Total Carrying Amount in Statement of Financial Position at December 31, 2014			Fair Value Estimate at December 31, 2014			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	14,369		$	14,808		$	—		$	—		$	14,808

	Derivatives- Interest rate contracts (b)	88			88			—			88			—

Total assets	$	14,457		$	14,896		$	—		$	88		$	14,808


Derivatives- Interest rate contracts (b)	$	10,368		$	10,368		$	—		$	10,368		$	—

Secured debt instruments- fixed rate: (c)
Mortgage notes payable	401,210			415,663			—			—			415,663

Fannie Mae credit facilities	568,086			606,623			—			—			606,623

Secured debt instruments- variable rate: (c)

Mortgage notes payable	31,337			31,337			—			—			31,337

Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

Fannie Mae credit facilities	266,196			266,196			—			—			266,196

Unsecured debt instruments: (c)
Commercial bank	152,500			152,500			—			—			152,500

Senior unsecured notes	2,069,076			2,144,125			—			—			2,144,125

Total liabilities	$	3,593,473		$	3,721,512		$	—		$	10,368		$	3,711,144


Redeemable noncontrolling interests in the Operating Partnership (d)	$	282,480		$	282,480		$	—		$	282,480		$	—



(a)	See Note 2, Significant Accounting Policies.

(b)	See Note 10, Derivatives and Hedging Activity.

(c)	See Note 6, Secured and Unsecured Debt.

(d)	See Note 8, Noncontrolling Interests.

There were no transfers into or out of each of the levels of the fair value hierarchy.
Financial Instruments Carried at Fair Value
The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. The fair values of interest rate options are determined using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates rise above the strike rate of the caps. The variable interest rates used in the calculation of projected receipts on the cap are based on an expectation of future interest rates derived from observable market interest rate curves and volatilities.
The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees.
Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. However, as of March 31, 2015 and December 31, 2014, the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. In conjunction with the FASB’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio.
Redeemable noncontrolling interests in the Operating Partnership have a redemption feature and are marked to their redemption value. The redemption value is based on the fair value of the Company’s common stock at the redemption date, and therefore, is calculated based on the fair value of the Company’s common stock at the balance sheet date. Since the valuation is based on observable inputs such as quoted prices for similar instruments in active markets, redeemable noncontrolling interests in the Operating Partnership are classified as Level 2.
Financial Instruments Not Carried at Fair Value
At March 31, 2015, the fair values of cash and cash equivalents, restricted cash, accounts receivable, prepaids, real estate taxes payable, accrued interest payable, security deposits and prepaid rent, distributions payable and accounts payable approximated their carrying values because of the short term nature of these instruments. The estimated fair values of other financial instruments were determined by the Company using available market information and appropriate valuation methodologies. Considerable judgment is necessary to interpret market data and develop estimated fair values. Accordingly, the estimates presented herein are not necessarily indicative of the amounts the Company would realize on the disposition of the financial instruments. The use of different market assumptions or estimation methodologies may have a material effect on the estimated fair value amounts.
We estimate the fair value of our notes receivable and debt instruments by discounting the remaining cash flows of the debt instrument at a discount rate equal to the replacement market credit spread plus the corresponding treasury yields. Factors considered in determining a replacement market credit spread include general market conditions, borrower specific credit spreads, time remaining to maturity, loan-to-value ratios and collateral quality, where applicable (Level 3).
We record impairment losses on long-lived assets used in operations when events and circumstances indicate that the assets might be impaired and the undiscounted cash flows estimated to be generated by the future operation and disposition of those assets are less than the net book value of those assets. Our cash flow estimates are based upon historical results adjusted to reflect our best estimate of future market and operating conditions and our estimated holding periods. The net book value of impaired assets is reduced to fair value. Our estimates of fair value represent our best estimate based upon Level 3 inputs such as industry trends and reference to market rates and transactions.
We consider various factors to determine if a decrease in the value of our investment in and advances to unconsolidated joint ventures, net is other-than-temporary. These factors include, but are not limited to, age of the venture, our intent and ability to retain our investment in the entity, the financial condition and long-term prospects of the entity, and the relationships with the other joint venture partners and its lenders. Based on the significance of the unobservable inputs, we classify these fair value measurements within Level 3 of the valuation hierarchy. The Company did not incur any other-than-temporary decrease in the value of its investments in unconsolidated joint ventures during the three months ended March 31, 2015 and 2014.
After determining an other-than-temporary decrease in the value of an equity method investment has occurred, we estimate the fair value of our investment by estimating the proceeds we would receive upon a hypothetical liquidation of the investment at the date of measurement. Inputs reflect management’s best estimate of what market participants would use in pricing the investment giving consideration to the terms of the joint venture agreement and the estimated discounted future cash flows to be generated from the underlying joint venture assets. The inputs and assumptions utilized to estimate the future cash flows of the underlying assets are based upon the Company’s evaluation of the economy, market trends, operating results, and other factors, including judgments regarding costs to complete any construction activities, lease up and occupancy rates, rental rates, inflation rates, capitalization rates utilized to estimate the projected cash flows at the disposition, and discount rates.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS	FAIR VALUE OF DERIVATIVES AND FINANCIAL INSTRUMENTS
	Fair value is based on the price that would be received to sell an asset or the exit price that would be paid to transfer a liability in an orderly transaction between market participants at the measurement date. A three-level valuation hierarchy prioritizes observable and unobservable inputs used to measure fair value. The fair value hierarchy consists of three broad levels, which are described below:

	•	Level 1 — Quoted prices in active markets for identical assets or liabilities that the entity has the ability to access.

	•	Level 2 — Observable inputs other than prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated with observable market data.

	•	Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
	The estimated fair values of the Operating Partnership’s financial instruments either recorded or disclosed on a recurring basis as of March 31, 2015 and December 31, 2014 are summarized as follows (dollars in thousands):


								Fair Value at March 31, 2015, Using
		Total Carrying Amount in Statement of Financial Position at March 31, 2015			Fair Value Estimate at March 31, 2015			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Derivatives - Interest rate contracts (a)	$	17		$	17		$	—		$	17		$	—

	Total assets	$	17		$	17		$	—		$	17		$	—


	Derivatives - Interest rate contracts (a)	$	686		$	686		$	—		$	686		$	—

	Secured debt instruments - fixed rate: (b)
	Mortgage notes payable	376,207			388,821			—			—			388,821

	Fannie Mae credit facilities	333,735			352,765			—			—			352,765

	Secured debt instruments - variable rate: (b)
	Tax-exempt secured notes payable	27,000			27,000			—			—			27,000

	Fannie Mae credit facilities	192,760			192,760			—			—			192,760

	Total liabilities	$	930,388		$	962,032		$	—		$	686		$	961,346



								Fair Value at December 31, 2014, Using
		Total Carrying Amount in Statement of Financial Position at December 31, 2014			Fair Value Estimate at December 31, 2014			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Derivatives - Interest rate contracts (a)	$	39		$	39		$	—		$	39		$	—

	Total assets	$	39		$	39		$	—		$	39		$	—


	Derivatives - Interest rate contracts (a)	$	918		$	918		$	—		$	918		$	—

	Secured debt instruments - fixed rate: (b)
	Mortgage notes payable	378,371			391,835			—			—			391,835

	Fannie Mae credit facilities	333,828			355,470			—			—			355,470

	Secured debt instruments - variable rate: (b)
	Tax-exempt secured notes payable	27,000			27,000			—			—			27,000

	Fannie Mae credit facilities	192,760			192,760			—			—			192,760

Total liabilities	$	932,877		$	967,983		$	—		$	918		$	967,065



(a)	See Note 7, Derivatives and Hedging Activity.

(b)	See Note 4, Debt.
Financial Instruments Carried at Fair Value
The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. The fair values of interest rate options are determined using the market standard methodology of discounting the future expected cash receipts that would occur if variable interest rates rise above the strike rate of the caps. The variable interest rates used in the calculation of projected receipts on the cap are based on an expectation of future interest rates derived from observable market interest rate curves and volatilities.
The General Partner, on behalf of the Operating Partnership, incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Operating Partnership has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees.
Although the General Partner, on behalf of the Operating Partnership, has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. However, as of March 31, 2015 and December 31, 2014, the Operating Partnership has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Operating Partnership has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy. In conjunction with the FASB’s fair value measurement guidance, the Operating Partnership made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio.
Financial Instruments Not Carried at Fair Value
As of March 31, 2015, the fair values of cash and cash equivalents, restricted cash, accounts receivable, prepaids, real estate taxes payable, accrued interest payable, security deposits and prepaid rent, distributions payable and accounts payable approximated their carrying values because of the short term nature of these instruments. The estimated fair values of other financial instruments were determined by the Operating Partnership using available market information and appropriate valuation methodologies. Considerable judgment is necessary to interpret market data and develop estimated fair values. Accordingly, the estimates presented herein are not necessarily indicative of the amounts the Operating Partnership would realize on the disposition of the financial instruments. The use of different market assumptions or estimation methodologies may have a material effect on the estimated fair value amounts.
Fair value of our debt instruments is estimated by discounting the remaining cash flows of the debt instrument at a discount rate equal to the replacement market credit spread plus the corresponding treasury yields. Factors considered in determining a replacement market credit spread include general market conditions, borrower specific credit spreads, time remaining to maturity, loan-to-value ratios and collateral quality (Level 3).
The Operating Partnership records impairment losses on long-lived assets used in operations when events and circumstances indicate that the assets might be impaired and the undiscounted cash flows estimated to be generated by the future operation and disposition of those assets are less than the net book value of those assets. Cash flow estimates are based upon historical results adjusted to reflect management’s best estimate of future market and operating conditions and our estimated holding periods. The net book value of impaired assets is reduced to fair value. The General Partner’s estimates of fair value represent management’s estimates based upon Level 3 inputs such as industry trends and reference to market rates and transactions.

Derivatives_and_Hedging_Activi

Derivatives and Hedging Activity	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	DERIVATIVES AND HEDGING ACTIVITY
	Risk Management Objective of Using Derivatives
	The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of its debt funding and through the use of derivative financial instruments. Specifically, the Company may enter into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing, and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to the Company’s investments and borrowings.
	Cash Flow Hedges of Interest Rate Risk
	The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Company primarily uses interest rate swaps and caps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Interest rate caps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an up front premium.
	The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in Accumulated other comprehensive income/(loss), net in the Consolidated Balance Sheets and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During the three months ended March 31, 2015 and 2014, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. During the three months ended March 31, 2015 and 2014, the Company recorded no ineffectiveness to earnings.
	Amounts reported in Accumulated other comprehensive income/(loss), net in the Consolidated Balance Sheets related to derivatives will be reclassified to interest expense as interest payments are made on the Company’s variable-rate debt. Through December 31, 2015, the Company estimates that an additional $6.3 million will be reclassified as an increase to interest expense.
	As of March 31, 2015, the Company had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		9		$	565,000

	Interest rate caps		3		$	243,079

	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, the Company had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		$	96,409


	Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet
	The tables below present the fair value of the Company’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Asset Derivatives								Liability Derivatives
		(included in *Other assets*)								(included in *Other liabilities*)
		Fair Value at:								Fair Value at:
		March 31,				December 31,				March 31,				December 31,
		2015				2014				2015				2014
	Derivatives designated as hedging instruments:
	Interest rate products	$	28			86				$	17,112			$	10,368

	Derivatives not designated as hedging instruments:
	Interest rate products	$	1			$	2			$	—			$	—

	Tabular Disclosure of the Effect of Derivative Instruments on the Consolidated Statements of Operations
	The tables below present the effect of the Company’s derivative financial instruments on the Consolidated Statements of Operations for the three months ended March 31, 2015 and 2014 (dollars in thousands):


	Derivatives in Cash Flow Hedging Relationships		Unrealized holding gain/(loss) Recognized in OCI								Gain/(Loss) Reclassified from Accumulated OCI into *Interest expense*								Gain/(Loss) Recognized in *Interest expense* (Ineffective Portion and Amount Excluded from Effectiveness Testing)
			(Effective Portion)								(Effective Portion)
			2015				2014				2015				2014				2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(7,552	)		$	(55	)		$	(737	)		$	(1,532	)		$	—			$	—




			Gain/(Loss) Recognized in *Interest and other income/(expense), net*
	Derivatives Not Designated as Hedging Instruments		2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(1	)		$	—

	Credit-risk-related Contingent Features
	The Company has agreements with some of its derivative counterparties that contain a provision where (1) if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations; or (2) the Company could be declared in default on its derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to the Company’s default on the indebtedness.
	Certain of the Company’s agreements with its derivative counterparties contain provisions where, if there is a change in the Company’s financial condition that materially changes the Company’s creditworthiness in an adverse manner, the Company may be required to fully collateralize its obligations under the derivative instrument.
	The Company also has an agreement with a derivative counterparty that incorporates the loan and financial covenant provisions of the Company’s indebtedness with a lender affiliate of the derivative counterparty. Failure to comply with these covenant provisions would result in the Company being in default on any derivative instrument obligations covered by the agreement.
	As of March 31, 2015, the fair value of derivatives in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $17.5 million. As of March 31, 2015, the Company has not posted any collateral related to these agreements. If the Company had breached any of these provisions at March 31, 2015, it may have been required to settle its obligations under the agreements at their termination value of $17.5 million.
	Tabular Disclosure of Offsetting Derivatives
	Company has elected not to offset derivative positions in the consolidated financial statements. The tables below present the effect on its financial position had the Company made the election to offset its derivative positions as of March 31, 2015 and December 31, 2014 (dollar in thousands):


Offsetting of Derivative Assets
	Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)				Gross Amounts Not Offset in the Consolidated Balance Sheets
													Financial Instruments				Cash Collateral Received				Net Amount
March 31, 2015	$	29			$	—			$	29			$	—			$	—			$	29


December 31, 2014	$	88			$	—			$	88			$	(27	)		$	—			$	61

(a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.


Offsetting of Derivative Liabilities
	Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)				Gross Amounts Not Offset in the Consolidated Balance Sheets
													Financial Instruments				Cash Collateral Posted				Net Amount
March 31, 2015	$	17,112			$	—			$	17,112			$	—			$	—			$	17,112


December 31, 2014	$	10,368			$	—			$	10,368			$	(27	)		$	—			$	10,341

(b) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.

Derivatives_and_Hedging_Activi1

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
DERIVATIVES AND HEDGING ACTIVITY	DERIVATIVES AND HEDGING ACTIVITY
	Risk Management Objective of Using Derivatives
	The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of its debt funding and through the use of derivative financial instruments. Specifically, the Company may enter into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing, and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to the Company’s investments and borrowings.
	Cash Flow Hedges of Interest Rate Risk
	The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Company primarily uses interest rate swaps and caps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Interest rate caps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an up front premium.
	The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in Accumulated other comprehensive income/(loss), net in the Consolidated Balance Sheets and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During the three months ended March 31, 2015 and 2014, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. During the three months ended March 31, 2015 and 2014, the Company recorded no ineffectiveness to earnings.
	Amounts reported in Accumulated other comprehensive income/(loss), net in the Consolidated Balance Sheets related to derivatives will be reclassified to interest expense as interest payments are made on the Company’s variable-rate debt. Through December 31, 2015, the Company estimates that an additional $6.3 million will be reclassified as an increase to interest expense.
	As of March 31, 2015, the Company had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		9		$	565,000
	Interest rate swaps		9		$	565,000
	Interest rate caps		3		$	243,079
	Interest rate caps		3		$	243,079
	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, the Company had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		$	96,409
	Interest rate caps		1		$	96,409

	Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet
	The tables below present the fair value of the Company’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Asset Derivatives								Liability Derivatives
		(included in *Other assets*)								(included in *Other liabilities*)
		Fair Value at:								Fair Value at:
		March 31,				December 31,				March 31,				December 31,
		2015				2014				2015				2014
	Derivatives designated as hedging instruments:
	Interest rate products	$	28			86				$	17,112			$	10,368
	Interest rate products	$	28			86				$	17,112			$	10,368
	Derivatives not designated as hedging instruments:
	Interest rate products	$	1			$	2			$	—			$	—
	Interest rate products	$	1			$	2			$	—			$	—
	Tabular Disclosure of the Effect of Derivative Instruments on the Consolidated Statements of Operations
	The tables below present the effect of the Company’s derivative financial instruments on the Consolidated Statements of Operations for the three months ended March 31, 2015 and 2014 (dollars in thousands):


	Derivatives in Cash Flow Hedging Relationships		Unrealized holding gain/(loss) Recognized in OCI								Gain/(Loss) Reclassified from Accumulated OCI into *Interest expense*								Gain/(Loss) Recognized in *Interest expense* (Ineffective Portion and Amount Excluded from Effectiveness Testing)
			(Effective Portion)								(Effective Portion)
			2015				2014				2015				2014				2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(7,552	)		$	(55	)		$	(737	)		$	(1,532	)		$	—			$	—
	Interest rate products		$	(7,552	)		$	(55	)		$	(737	)		$	(1,532	)		$	—			$	—



			Gain/(Loss) Recognized in *Interest and other income/(expense), net*
	Derivatives Not Designated as Hedging Instruments		2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(1	)		$	—
	Interest rate products		$	(1	)		$	—
	Credit-risk-related Contingent Features
	The Company has agreements with some of its derivative counterparties that contain a provision where (1) if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations; or (2) the Company could be declared in default on its derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to the Company’s default on the indebtedness.
	Certain of the Company’s agreements with its derivative counterparties contain provisions where, if there is a change in the Company’s financial condition that materially changes the Company’s creditworthiness in an adverse manner, the Company may be required to fully collateralize its obligations under the derivative instrument.
	The Company also has an agreement with a derivative counterparty that incorporates the loan and financial covenant provisions of the Company’s indebtedness with a lender affiliate of the derivative counterparty. Failure to comply with these covenant provisions would result in the Company being in default on any derivative instrument obligations covered by the agreement.
	As of March 31, 2015, the fair value of derivatives in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $17.5 million. As of March 31, 2015, the Company has not posted any collateral related to these agreements. If the Company had breached any of these provisions at March 31, 2015, it may have been required to settle its obligations under the agreements at their termination value of $17.5 million.
	Tabular Disclosure of Offsetting Derivatives
	Company has elected not to offset derivative positions in the consolidated financial statements. The tables below present the effect on its financial position had the Company made the election to offset its derivative positions as of March 31, 2015 and December 31, 2014 (dollar in thousands):


Offsetting of Derivative Assets
	Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)				Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Received				Net Amount
March 31, 2015	$	29			$	—			$	29			$	—			$	—			$	29
March 31, 2015	$	29			$	—			$	29			$	—			$	—			$	29

December 31, 2014	$	88			$	—			$	88			$	(27	)		$	—			$	61
December 31, 2014	$	88			$	—			$	88			$	(27	)		$	—			$	61
(a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.


Offsetting of Derivative Liabilities
	Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)				Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Posted				Net Amount
March 31, 2015	$	17,112			$	—			$	17,112			$	—			$	—			$	17,112
March 31, 2015	$	17,112			$	—			$	17,112			$	—			$	—			$	17,112

December 31, 2014	$	10,368			$	—			$	10,368			$	(27	)		$	—			$	10,341
December 31, 2014	$	10,368			$	—			$	10,368			$	(27	)		$	—			$	10,341
(b) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
DERIVATIVES AND HEDGING ACTIVITY	DERIVATIVES AND HEDGING ACTIVITY
	Risk Management Objective of Using Derivatives
	The Operating Partnership is exposed to certain risks arising from both its business operations and economic conditions. The General Partner principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The General Partner manages economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of its debt funding and through the use of derivative financial instruments. Specifically, the General Partner enters into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The General Partner’s and the Operating Partnership’s derivative financial instruments are used to manage differences in the amount, timing, and duration of the General Partner’s known or expected cash payments principally related to the General Partner’s borrowings.
	Cash Flow Hedges of Interest Rate Risk
	The General Partner’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the General Partner primarily uses interest rate swaps and caps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for the General Partner making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. Interest rate caps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty if interest rates rise above the strike rate on the contract in exchange for an up front premium.
	A portion of the General Partner’s interest rate derivatives have been allocated to the Operating Partnership based on the General Partner’s underlying debt instruments allocated to the Operating Partnership. (See Note 4, Debt.)
	The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in Accumulated other comprehensive income/(loss), net in the Consolidated Balance Sheets and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During the three months ended March 31, 2015 and 2014, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. The Operating Partnership recorded no gain or loss from ineffectiveness during the three months ended March 31, 2015 and 2014.
	Amounts reported in Accumulated other comprehensive income/(loss), net related to derivatives will be reclassified to interest expense as interest payments are made on the General Partner’s variable-rate debt that is allocated to the Operating Partnership. Through December 31, 2015, we estimate that an additional $691,000 will be reclassified as an increase to interest expense.
	As of March 31, 2015, the Operating Partnership had the following outstanding interest rate derivatives designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		1		$	46,272
	Interest rate swaps		1		$	46,272
	Interest rate caps		2		$	166,341
	Interest rate caps		2		$	166,341
	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, we had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		89,220
	Interest rate caps		1		89,220
	Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet
	The table below presents the fair value of the Operating Partnership’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Asset Derivatives								Liability Derivatives
		(included in *Other assets*)								(included in *Other liabilities*)
		Fair Value at:								Fair Value at:
		March 31,				December 31,				March 31,				December 31,
		2015				2014				2015				2014
	Derivatives designated as hedging instruments:
	Interest rate products	$	16			$	37			$	686			$	918
	Interest rate products	$	16			$	37			$	686			$	918

	Derivatives not designated as hedging instruments:
	Interest rate products	$	1			$	2			$	—			$	—
	Interest rate products	$	1			$	2			$	—			$	—

	Tabular Disclosure of the Effect of Derivative Instruments on the Consolidated Statements of Operations
	The tables below present the effect of the derivative financial instruments on the Consolidated Statements of Operations for the three months ended March 31, 2015 and 2014 (dollars in thousands):


			Unrealized holding gain/(loss) Recognized in OCI								Gain/(Loss) Reclassified from Accumulated OCI into *Interest expense*
			(Effective Portion)								(Effective Portion)
	Derivatives in Cash Flow Hedging Relationships		2015				2014				2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(51	)		$	(51	)		$	(286	)		$	(623	)



			Gain/(Loss) Recognized in
			Interest and other income/(expense), net
	Derivatives Not Designated as Hedging Instruments		2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(1	)		$	—
	Interest rate products		$	(1	)		$	—
	Credit-risk-related Contingent Features
	The General Partner has agreements with some of its derivative counterparties that contain a provision where (1) if the General Partner defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the General Partner could also be declared in default on its derivative obligations; or (2) the General Partner could be declared in default on its derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to the General Partner’s default on the indebtedness.
	Certain of the General Partner’s agreements with its derivative counterparties contain provisions where if there is a change in the General Partner’s financial condition that materially changes the General Partner’s creditworthiness in an adverse manner, the General Partner may be required to fully collateralize its obligations under the derivative instrument. At March 31, 2015 and December 31, 2014, no cash collateral was posted or required to be posted by the General Partner or by a counterparty.
	The General Partner also has an agreement with a derivative counterparty that incorporates the loan and financial covenant provisions of the General Partner’s indebtedness with a lender affiliate of the derivative counterparty. Failure to comply with these covenant provisions would result in the General Partner being in default on any derivative instrument obligations covered by the agreement.
	The General Partner has certain agreements with some of its derivative counterparties that contain a provision where in the event of default by the General Partner or the counterparty, the right of setoff may be exercised. Any amount payable to one party by the other party may be reduced by its setoff against any amounts payable by the other party. Events that give rise to default by either party may include, but are not limited to, the failure to pay or deliver payment under the derivative contract, the failure to comply with or perform under the derivative agreement, bankruptcy, a merger without assumption of the derivative agreement, or in a merger, a surviving entity’s creditworthiness is materially weaker than the original party to the derivative agreement.
	As of March 31, 2015, the fair value of derivatives in a net liability position that were allocated to the Operating Partnership, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $774,000. As of March 31, 2015, the General Partner has not posted any collateral related to these agreements. If the General Partner had breached any of these provisions at March 31, 2015, it would have been required to settle its obligations under the agreements at their termination value of $774,000.
The General Partner has elected not to offset derivative positions in the consolidated financial statements. The table below presents the effect on the Operating Partnership’s financial position had the General Partner made the election to offset its derivative positions as of March 31, 2015 and December 31, 2014:


Offsetting of Derivative Assets
	Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)				Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Received				Net Amount
March 31, 2015	$	17			$	—			$	17			$	—			$	—			$	17
March 31, 2015	$	17			$	—			$	17			$	—			$	—			$	17

December 31, 2014	$	39			$	—			$	39			$	—			$	—			$	39
December 31, 2014	$	39			$	—			$	39			$	—			$	—			$	39
(a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.


Offsetting of Derivative Liabilities
	Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)				Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Posted				Net Amount
March 31, 2015	$	686			$	—			$	686			$	—			$	—			$	686
March 31, 2015	$	686			$	—			$	686			$	—			$	—			$	686

December 31, 2014	$	918			$	—			$	918			$	—			$	—			$	918
December 31, 2014	$	918			$	—			$	918			$	—			$	—			$	918
(b) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.

Stock_Based_Compensation

Stock Based Compensation	3 Months Ended
Stock Based Compensation	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK BASED COMPENSATION	STOCK BASED COMPENSATION
STOCK BASED COMPENSATION	The Company recognized stock based compensation expense, inclusive of awards granted to our independent directors, of $4.5 million and $3.7 million during the three months ended March 31, 2015 and 2014, respectively.

Capital_Structure_UNITED_DOMIN

Capital Structure (UNITED DOMINION REALTY, L.P.) (United Dominion Reality L.P. [Member])	3 Months Ended
	Mar. 31, 2015
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
CAPITAL STRUCTURE	CAPITAL STRUCTURE
	General Partnership Units
	The General Partner has complete discretion to manage and control the operations and business of the Operating Partnership, which includes but is not limited to the acquisition and disposition of real property, construction of buildings and making capital improvements, and the borrowing of funds from outside lenders or UDR and its subsidiaries to finance such activities. The General Partner can generally authorize, issue, sell, redeem or purchase any OP Unit or securities of the Operating Partnership without the approval of the limited partners. The General Partner can also approve, with regard to the issuances of OP Units, the class or one or more series of classes, with designations, preferences, participating, optional or other special rights, powers and duties including rights, powers and duties senior to limited partnership interests without approval of any limited partners except holders of Class A Limited Partnership Units. There were 110,883 General Partnership units outstanding at March 31, 2015 and December 31, 2014, all of which were held by UDR.
	Limited Partnership Units
	As of March 31, 2015 and December 31, 2014, there were 183,167,815 limited partnership units outstanding, of which 1,873,332 were Class A Limited Partnership Units. UDR owned 174,002,876, or 95.0% of, and 174,002,342, or 95.0% of, OP Units outstanding at March 31, 2015 and December 31, 2014, respectively, of which 121,661 were Class A Limited Partnership Units. The remaining 9,164,939, or 5.0% of, and 9,165,473, or 5.0% of, OP Units outstanding, were held by non-affiliated partners at March 31, 2015 and December 31, 2014, respectively, of which 1,751,671 were Class A Limited Partnership Units.
	Subject to the terms of the Operating Partnership Agreement, the limited partners have the right to require the Operating Partnership to redeem all or a portion of the OP Units held by the limited partner at a redemption price equal to and in the form of the Cash Amount (as defined in the Operating Partnership Agreement), provided that such OP Units have been outstanding for at least one year. UDR, as general partner of the Operating Partnership may, in its sole discretion, purchase the OP Units by paying to the limited partner either the Cash Amount or the REIT Share Amount (generally one share of common stock of UDR for each OP Unit), as defined in the Operating Partnership Agreement.
	The non-affiliated limited partners’ capital is adjusted to redemption value at the end of each reporting period with the corresponding offset against UDR’s limited partner capital account based on the redemption rights noted above. The aggregate value upon redemption of the then-outstanding OP Units held by limited partners was $311.9 million and $282.5 million as of March 31, 2015 and December 31, 2014, respectively, based on the value of UDR’s common stock at each period end. A limited partner has no right to receive any distributions from the Operating Partnership on or after the date of redemption of its OP Units.
	Class A Limited Partnership Units
	Class A Limited Partnership Units have a cumulative, annual, non-compounded preferred return, which is equal to 8% based on a value of $16.61 per Class A Limited Partnership Unit.
	Holders of the Class A Limited Partnership Units exclusively possess certain voting rights. The Operating Partnership may not do the following without approval of the holders of the Class A Limited Partnership Units: (i) increase the authorized or issued amount of Class A Limited Partnership Units, (ii) reclassify any other partnership interest into Class A Limited Partnership Units, (iii) create, authorize or issue any obligations or security convertible into or the right to purchase any Class A Limited Partnership units, (iv) enter into a merger or acquisition, or (v) amend or modify the Agreement of Limited Partnership of the Operating Partnership in a manner that adversely affects the relative rights, preferences or privileges of the Class A Limited Partnership Units.
	Allocation of Profits and Losses
	Profit of the Operating Partnership is allocated in the following order: (i) to the General Partner and the Limited Partners in proportion to and up to the amount of cash distributions made during the year, and (ii) to the General Partner and Limited Partners in accordance with their percentage interests. Losses and depreciation and amortization expenses, non-recourse liabilities are allocated to the General Partner and Limited Partners in accordance with their percentage interests. Losses allocated to the Limited Partners are capped to the extent that such an allocation would not cause a deficit in the Limited Partners’ capital account. Such losses are, therefore, allocated to the General Partner. If any Partner’s capital balance were to fall into a deficit, any income and gains are allocated to each Partner sufficient to eliminate its negative capital balance.

Commitments_and_Contingencies

Commitments and Contingencies

3 Months Ended

Mar. 31, 2015

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Commitments

Real Estate Under Development

The following summarizes the Company’s real estate commitments at March 31, 2015 (dollars in thousands):

Number of

Costs Incurred

Expected Costs

Average Ownership

Properties

to Date (a)

to Complete

Stake

Wholly-owned — under development

196,653

(b)

21,047

100

Wholly-owned — redevelopment

90,382

(b)

22,618

100

Joint ventures:

Unconsolidated joint ventures

285,730

189,037

(c)

Various

Participating loan investments

75,647

(d)

16,362

(e)

648,412

249,064

(a)

Represents 100% of project costs incurred to date.

(b)

Costs incurred to date include $11.1 million and $2.3 million of accrued fixed assets for development and redevelopment, respectively.

(c)

Represents UDR’s proportionate share of expected remaining costs to complete.

(d)

Represents the participating loan balance funded as of March 31, 2015.

(e)

Represents UDR’s remaining participating loan commitment for Steele Creek.

Contingencies

Litigation and Legal Matters

The Company is subject to various legal proceedings and claims arising in the ordinary course of business. The Company cannot determine the ultimate liability with respect to such legal proceedings and claims at this time. The Company believes that such liability, to the extent not provided for through insurance or otherwise, will not have a material adverse effect on our financial condition, results of operations or cash flow.

Commitments_and_Contingencies_

Commitments and Contingencies (UNITED DOMINION REALTY, L.P.) Commitments and Contingencies (UNITED DOMINION REALTY, L.P.)

3 Months Ended

Mar. 31, 2015

Entity Information [Line Items]

COMMITMENTS AND CONTINGENCIES

Commitments

Real Estate Under Development

The following summarizes the Company’s real estate commitments at March 31, 2015 (dollars in thousands):

Number of

Costs Incurred

Expected Costs

Average Ownership

Properties

to Date (a)

to Complete

Stake

Wholly-owned — under development

196,653

(b)

21,047

100

Wholly-owned — redevelopment

90,382

(b)

22,618

100

Joint ventures:

Unconsolidated joint ventures

285,730

189,037

(c)

Various

Participating loan investments

75,647

(d)

16,362

(e)

648,412

249,064

(a)

Represents 100% of project costs incurred to date.

(b)

Costs incurred to date include $11.1 million and $2.3 million of accrued fixed assets for development and redevelopment, respectively.

(c)

Represents UDR’s proportionate share of expected remaining costs to complete.

(d)

Represents the participating loan balance funded as of March 31, 2015.

(e)

Represents UDR’s remaining participating loan commitment for Steele Creek.

Contingencies

Litigation and Legal Matters

United Dominion Reality L.P. [Member]

Entity Information [Line Items]

COMMITMENTS AND CONTINGENCIES

Commitments

Real Estate Under Development

The following summarizes the Operating Partnership’s real estate commitments at March 31, 2015 (dollars in thousands):

Number of

Costs Incurred

Expected Costs

Properties

to Date (a)

to Complete (unaudited)

Real estate communities — redevelopment

2,310

12,690

(a)

Costs incurred to date include $515,000 of accrued fixed assets for redevelopment.

Contingencies

Litigation and Legal Matters

The Operating Partnership is subject to various legal proceedings and claims arising in the ordinary course of business. The Operating Partnership cannot determine the ultimate liability with respect to such legal proceedings and claims at this time. The General Partner believes that such liability, to the extent not provided for through insurance or otherwise, will not have a material adverse effect on the Operating Partnership’s financial condition, results of operations or cash flow.

Reportable_Segments

Reportable Segments	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
REPORTABLE SEGMENTS	REPORTABLE SEGMENTS
	GAAP guidance requires that segment disclosures present the measure(s) used by the chief operating decision maker to decide how to allocate resources and for purposes of assessing such segments’ performance. UDR’s chief operating decision maker is comprised of several members of its executive management team who use several generally accepted industry financial measures to assess the performance of the business for our reportable operating segments.
	UDR owns and operates multifamily apartment communities that generate rental and other property related income through the leasing of apartment homes to a diverse base of tenants. The primary financial measures for UDR’s apartment communities are rental income and net operating income (“NOI”). Rental income represents gross market rent less adjustments for concessions, vacancy loss and bad debt. NOI is defined as rental income less direct property rental expenses. Rental expenses include real estate taxes, insurance, personnel, utilities, repairs and maintenance, administrative and marketing. Excluded from NOI is property management expense, which is calculated as 2.75% of property revenue to cover the regional supervision and accounting costs related to consolidated property operations, and land rent. UDR’s chief operating decision maker utilizes NOI as the key measure of segment profit or loss.
	UDR’s two reportable segments are Same-Store Communities and Non-Mature Communities/Other:


	•	Same-Store Communities represent those communities acquired, developed, and stabilized prior to January 1, 2014 and held as of March 31, 2015. A comparison of operating results from the prior year is meaningful as these communities were owned and had stabilized occupancy and operating expenses as of the beginning of the prior period, there is no plan to conduct substantial redevelopment activities, and the community is not held for disposition within the current year. A community is considered to have stabilized occupancy once it achieves 90% occupancy for at least three consecutive months.


	•	Non-Mature Communities/Other represent those communities that do not meet the criteria to be included in Same-Store Communities, including, but not limited to, recently acquired, developed and redeveloped properties, and the non-apartment components of mixed use properties.
	Management evaluates the performance of each of our apartment communities on a Same-Store Community and Non-Mature Community/Other basis, as well as individually and geographically. This is consistent with the aggregation criteria under GAAP as each of our apartment communities generally has similar economic characteristics, facilities, services, and tenants. Therefore, the Company’s reportable segments have been aggregated by geography in a manner identical to that which is provided to the chief operating decision maker.
	All revenues are from external customers and no single tenant or related group of tenants contributed 10% or more of UDR’s total revenues during the three months ended March 31, 2015 and 2014.
	The following table details rental income and NOI from continuing and discontinued operations for UDR’s reportable segments for the three months ended March 31, 2015 and 2014, and reconciles NOI to Net Income/(Loss) Attributable to UDR, Inc. in the Consolidated Statements of Operations (dollars in thousands):


		Three Months Ended
		March 31, (a)
		2015				2014
	Reportable apartment home segment rental income
	Same-Store Communities
	West Region	$	67,857			$	63,267

	Mid-Atlantic Region	42,795				42,049

	Southeast Region	27,829				26,497

	Northeast Region	20,892				19,803

	Southwest Region	14,107				13,467

	Non-Mature Communities/Other	33,567				29,317

	Total consolidated rental income	$	207,047			$	194,400


	Reportable apartment home segment NOI
	Same-Store Communities
	West Region	$	50,228			$	45,408

	Mid-Atlantic Region	29,288				28,835

	Southeast Region	18,547				17,872

	Northeast Region	15,566				14,546

	Southwest Region	8,536				8,358

	Non-Mature Communities/Other	21,410				17,105

	Total consolidated NOI	143,575				132,124

	Reconciling items:
	Joint venture management and other fees	12,706				3,687

	Property management	(5,694		)		(5,346		)
	Other operating expenses	(1,766		)		(1,935		)
	Real estate depreciation and amortization	(88,777		)		(88,533		)
	General and administrative	(12,152		)		(11,994		)
	Casualty-related recoveries/(charges), net	(996		)		(500		)
	Other depreciation and amortization	(1,623		)		(1,080		)
	Income/(loss) from unconsolidated entities	59,159				(3,565		)

	Interest expense	(28,800		)		(32,884		)
	Interest and other income/(expense), net	360				1,415

Tax benefit/(expense), net	425				3,329

Gain/(loss) on sale of real estate owned, net of tax	—				24,294

Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership	(2,588		)		(647		)
Net (income)/loss attributable to noncontrolling interests	(7		)		(4		)
Net income/(loss) attributable to UDR, Inc.	$	73,822			$	18,361



(a)	Same-Store Community population consisted of 36,063 apartment homes.

The following table details the assets of UDR’s reportable segments as of March 31, 2015 and December 31, 2014 (dollars in thousands):


	March 31,				December 31,
	2015				2014
Reportable apartment home segment assets:
Same-Store Communities:
West Region	$	2,626,770			$	2,620,242

Mid-Atlantic Region	1,536,389				1,533,993

Southeast Region	788,668				786,438

Northeast Region	1,078,431				1,076,656

Southwest Region	441,888				440,721

Non-Mature Communities/Other	1,981,502				1,925,209

Total assets	8,453,648				8,383,259

Accumulated depreciation	(2,522,100		)		(2,434,772		)
Total assets — net book value	5,931,548				5,948,487

Reconciling items:
Cash and cash equivalents	6,274				15,224

Restricted cash	23,266				22,340

Deferred financing costs, net	21,676				22,686

Notes receivable, net	15,494				14,369

Investment in and advances to unconsolidated joint ventures, net	763,540				718,226

Other assets	96,713				105,202

Total consolidated assets	$	6,858,511			$	6,846,534

Capital expenditures related to our Same-Store Communities totaled $13.3 million and $7.7 million for the three months ended March 31, 2015 and 2014, respectively. Capital expenditures related to our Non-Mature Communities/Other totaled $2.5 million and $2.1 million for the three months ended March 31, 2015 and 2014.
Markets included in the above geographic segments are as follows:

i.	West Region — Orange County, San Francisco, Seattle, Los Angeles, Monterey Peninsula, Other Southern California, and Portland

ii.	Mid-Atlantic Region — Metropolitan D.C., Baltimore, Richmond, Norfolk, and Other Mid-Atlantic

iii.	Southeast Region — Tampa, Orlando, Nashville, and Other Florida

iv.	Northeast Region — New York and Boston

v.	Southwest Region — Dallas and Austin

Reportable_Segments_UNITED_DOM

Reportable Segments (UNITED DOMINION REALTY, L.P.)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
REPORTABLE SEGMENTS	REPORTABLE SEGMENTS
	GAAP guidance requires that segment disclosures present the measure(s) used by the chief operating decision maker to decide how to allocate resources and for purposes of assessing such segments’ performance. UDR’s chief operating decision maker is comprised of several members of its executive management team who use several generally accepted industry financial measures to assess the performance of the business for our reportable operating segments.
	UDR owns and operates multifamily apartment communities that generate rental and other property related income through the leasing of apartment homes to a diverse base of tenants. The primary financial measures for UDR’s apartment communities are rental income and net operating income (“NOI”). Rental income represents gross market rent less adjustments for concessions, vacancy loss and bad debt. NOI is defined as rental income less direct property rental expenses. Rental expenses include real estate taxes, insurance, personnel, utilities, repairs and maintenance, administrative and marketing. Excluded from NOI is property management expense, which is calculated as 2.75% of property revenue to cover the regional supervision and accounting costs related to consolidated property operations, and land rent. UDR’s chief operating decision maker utilizes NOI as the key measure of segment profit or loss.
	UDR’s two reportable segments are Same-Store Communities and Non-Mature Communities/Other:


	•	Same-Store Communities represent those communities acquired, developed, and stabilized prior to January 1, 2014 and held as of March 31, 2015. A comparison of operating results from the prior year is meaningful as these communities were owned and had stabilized occupancy and operating expenses as of the beginning of the prior period, there is no plan to conduct substantial redevelopment activities, and the community is not held for disposition within the current year. A community is considered to have stabilized occupancy once it achieves 90% occupancy for at least three consecutive months.


	•	Non-Mature Communities/Other represent those communities that do not meet the criteria to be included in Same-Store Communities, including, but not limited to, recently acquired, developed and redeveloped properties, and the non-apartment components of mixed use properties.
	Management evaluates the performance of each of our apartment communities on a Same-Store Community and Non-Mature Community/Other basis, as well as individually and geographically. This is consistent with the aggregation criteria under GAAP as each of our apartment communities generally has similar economic characteristics, facilities, services, and tenants. Therefore, the Company’s reportable segments have been aggregated by geography in a manner identical to that which is provided to the chief operating decision maker.
	All revenues are from external customers and no single tenant or related group of tenants contributed 10% or more of UDR’s total revenues during the three months ended March 31, 2015 and 2014.
	The following table details rental income and NOI from continuing and discontinued operations for UDR’s reportable segments for the three months ended March 31, 2015 and 2014, and reconciles NOI to Net Income/(Loss) Attributable to UDR, Inc. in the Consolidated Statements of Operations (dollars in thousands):


		Three Months Ended
		March 31, (a)
		2015				2014
	Reportable apartment home segment rental income
	Same-Store Communities
	West Region	$	67,857			$	63,267

	Mid-Atlantic Region	42,795				42,049

	Southeast Region	27,829				26,497

	Northeast Region	20,892				19,803

	Southwest Region	14,107				13,467

	Non-Mature Communities/Other	33,567				29,317

	Total consolidated rental income	$	207,047			$	194,400


	Reportable apartment home segment NOI
	Same-Store Communities
	West Region	$	50,228			$	45,408

	Mid-Atlantic Region	29,288				28,835

	Southeast Region	18,547				17,872

	Northeast Region	15,566				14,546

	Southwest Region	8,536				8,358

	Non-Mature Communities/Other	21,410				17,105

	Total consolidated NOI	143,575				132,124

	Reconciling items:
	Joint venture management and other fees	12,706				3,687

	Property management	(5,694		)		(5,346		)
	Other operating expenses	(1,766		)		(1,935		)
	Real estate depreciation and amortization	(88,777		)		(88,533		)
	General and administrative	(12,152		)		(11,994		)
	Casualty-related recoveries/(charges), net	(996		)		(500		)
	Other depreciation and amortization	(1,623		)		(1,080		)
	Income/(loss) from unconsolidated entities	59,159				(3,565		)

	Interest expense	(28,800		)		(32,884		)
	Interest and other income/(expense), net	360				1,415

Tax benefit/(expense), net	425				3,329

Gain/(loss) on sale of real estate owned, net of tax	—				24,294

Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership	(2,588		)		(647		)
Net (income)/loss attributable to noncontrolling interests	(7		)		(4		)
Net income/(loss) attributable to UDR, Inc.	$	73,822			$	18,361



(a)	Same-Store Community population consisted of 36,063 apartment homes.

The following table details the assets of UDR’s reportable segments as of March 31, 2015 and December 31, 2014 (dollars in thousands):


	March 31,				December 31,
	2015				2014
Reportable apartment home segment assets:
Same-Store Communities:
West Region	$	2,626,770			$	2,620,242

Mid-Atlantic Region	1,536,389				1,533,993

Southeast Region	788,668				786,438

Northeast Region	1,078,431				1,076,656

Southwest Region	441,888				440,721

Non-Mature Communities/Other	1,981,502				1,925,209

Total assets	8,453,648				8,383,259

Accumulated depreciation	(2,522,100		)		(2,434,772		)
Total assets — net book value	5,931,548				5,948,487

Reconciling items:
Cash and cash equivalents	6,274				15,224

Restricted cash	23,266				22,340

Deferred financing costs, net	21,676				22,686

Notes receivable, net	15,494				14,369

Investment in and advances to unconsolidated joint ventures, net	763,540				718,226

Other assets	96,713				105,202

Total consolidated assets	$	6,858,511			$	6,846,534

Capital expenditures related to our Same-Store Communities totaled $13.3 million and $7.7 million for the three months ended March 31, 2015 and 2014, respectively. Capital expenditures related to our Non-Mature Communities/Other totaled $2.5 million and $2.1 million for the three months ended March 31, 2015 and 2014.
Markets included in the above geographic segments are as follows:

i.	West Region — Orange County, San Francisco, Seattle, Los Angeles, Monterey Peninsula, Other Southern California, and Portland

ii.	Mid-Atlantic Region — Metropolitan D.C., Baltimore, Richmond, Norfolk, and Other Mid-Atlantic

iii.	Southeast Region — Tampa, Orlando, Nashville, and Other Florida

iv.	Northeast Region — New York and Boston

v.	Southwest Region — Dallas and Austin
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
REPORTABLE SEGMENTS	REPORTABLE SEGMENTS
	GAAP guidance requires that segment disclosures present the measure(s) used by the chief operating decision maker to decide how to allocate resources and for purposes of assessing such segments’ performance. The Operating Partnership has the same chief operating decision maker as that of its parent, the General Partner. The chief operating decision maker consists of several members of UDR’s executive management team who use several generally accepted industry financial measures to assess the performance of the business for our reportable operating segments.
	The Operating Partnership owns and operates multifamily apartment communities throughout the United States that generate rental and other property related income through the leasing of apartment homes to a diverse base of tenants. The primary financial measures of the Operating Partnership’s apartment communities are rental income and net operating income (“NOI”), and are included in the chief operating decision maker’s assessment of the Operating Partnership’s performance on a consolidated basis. Rental income represents gross market rent less adjustments for concessions, vacancy loss and bad debt. NOI is defined as total revenues less direct property operating expenses. Rental expenses include real estate taxes, insurance, personnel, utilities, repairs and maintenance, administrative and marketing. Excluded from NOI is property management expense which is calculated as 2.75% of property revenue to cover the regional supervision and accounting costs related to consolidated property operations, and land rent. The chief operating decision maker of the General Partner utilizes NOI as the key measure of segment profit or loss.
	The Operating Partnership’s two reportable segments are Same-Store Communities and Non-Mature Communities/Other:


	•	Same-Store Communities represent those communities acquired, developed, and stabilized prior to January 1, 2014 and held as of March 31, 2015. A comparison of operating results from the prior year is meaningful as these communities were owned and had stabilized occupancy and operating expenses as of the beginning of the prior period, there is no plan to conduct substantial redevelopment activities, and the community is not held for disposition within the current year. A community is considered to have stabilized occupancy once it achieves 90% occupancy for at least three consecutive months.


	•	Non-Mature Communities/Other represent those communities that do not meet the criteria to be included in Same-Store Communities, including, but not limited to, recently acquired, developed and redeveloped properties, and the non-apartment components of mixed use properties.
	Management of the General Partner evaluates the performance of each of the Operating Partnership’s apartment communities on a Same-Store Community and Non-Mature Community/Other basis, as well as individually and geographically. This is consistent with the aggregation criteria under GAAP as each of the apartment communities generally has similar economic characteristics, facilities, services, and tenants. Therefore, the Operating Partnership’s reportable segments have been aggregated by geography in a manner identical to that which is provided to the chief operating decision maker.
	All revenues are from external customers and no single tenant or related group of tenants contributed 10% or more of the Operating Partnership’s total revenues during the three months ended March 31, 2015 and 2014.
	The following table details rental income and NOI from continuing and discontinued operations for the Operating Partnership’s reportable segments for the three months ended March 31, 2015 and 2014, and reconciles NOI to Net income/(loss) attributable to OP unitholders in the Consolidated Statements of Operations (dollars in thousands):


		Three Months Ended
		March 31, (a)
		2015				2014
	Reportable apartment home segment rental income
	Same-Store Communities
	West Region	$	47,815			$	44,238

	Mid-Atlantic Region	17,249				17,246

	Southeast Region	11,679				11,131

	Northeast Region	15,072				14,268

	Southwest Region	6,737				6,553

	Non-Mature Communities/Other	11,543				8,934

	Total consolidated rental income	$	110,095			$	102,370

	Reportable apartment home segment NOI
	Same-Store Communities
	West Region	$	35,277			$	32,089

	Mid-Atlantic Region	11,466				11,565

	Southeast Region	7,710				7,457

	Northeast Region	11,572				10,638

	Southwest Region	4,213				4,217

	Non-Mature Communities/Other	7,877				6,451

	Total consolidated NOI	78,115				72,417

	Reconciling items:
	Property management	(3,027		)		(2,815		)
	Other operating expenses	(1,490		)		(1,436		)
	Real estate depreciation and amortization	(44,478		)		(44,271		)
	General and administrative	(5,639		)		(6,970		)
	Casualty-related recoveries/(charges), net	(593		)		(500		)
	Interest expense	(10,771		)		(10,014		)
	Gain/(loss) on sale of real estate owned	24,623				24,402

	Net (income)/loss attributable to noncontrolling interests	(394		)		(280		)
	Net income/(loss) attributable to OP unitholders	$	36,346			$	30,533



(a)	Same-store consists of 19,209 apartment homes.
The following table details the assets of the Operating Partnership’s reportable segments as of March 31, 2015 and December 31, 2014 (dollars in thousands):


	March 31,				December 31, 2014
	2015
Reportable apartment home segment assets
Same-Store Communities
West Region	$	1,690,647			$	1,686,127

Mid-Atlantic Region	714,425				713,093

Southeast Region	334,282				333,428

Northeast Region	778,378				777,376

Southwest Region	229,627				228,996

Non-Mature Communities/Other	501,436				499,750

Total assets	4,248,795				4,238,770

Accumulated depreciation	(1,447,513		)		(1,403,303		)
Total assets - net book value	2,801,282				2,835,467

Reconciling items:
Cash and cash equivalents	826				502

Restricted cash	14,441				13,811

Deferred financing costs, net	4,118				4,475

Other assets	22,714				24,029

Total consolidated assets	$	2,843,381			$	2,878,284

Capital expenditures related to the Operating Partnership’s Same-Store Communities totaled $7.9 million and $3.9 million for the three months ended March 31, 2015 and 2014, respectively. Capital expenditures related to the Operating Partnership’s Non-Mature Communities/Other totaled $472,000 and $256,000 for the three months ended March 31, 2015 and 2014, respectively.
Markets included in the above geographic segments are as follows:

i.	West Region — Orange County, San Francisco, Seattle, Los Angeles, Monterey Peninsula, Other Southern California, and Portland

ii.	Mid-Atlantic Region — Metropolitan D.C. and Baltimore

iii.	Southeast Region — Tampa, Nashville, and Other Florida

iv.	Northeast Region — New York and Boston

v.	Southwest Region — Dallas

Significant_Accounting_Policie2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income/(Loss)
	Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to stockholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three months ended March 31, 2015 and 2014, the Company’s other comprehensive income/(loss) consisted of the gain/(loss) (effective portion) on derivative instruments that are designated as and qualify as cash flow hedges, (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) into earnings, and the allocation of other comprehensive income/(loss) to redeemable noncontrolling interests. The (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) is included in Interest expense on the Consolidated Statements of Operations. See Note 10, Derivatives and Hedging Activity, for further discussion. The allocation of other comprehensive income/(loss) to redeemable noncontrolling interests was $(225,000) and $56,000 during the three months ended March 31, 2015 and 2014, respectively.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The standard specifically excludes lease contracts. The ASU allows for the use of either the full or modified retrospective transition method, and the standard will be effective for the Company on January 1, 2017; early adoption is not permitted. The Company has not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.
	Discontinued Operations
	In accordance with GAAP, a discontinued operation represents (1) a component of an entity or group of components that has been disposed of or is classified as held for sale in a single transaction and represents a strategic shift that has or will have a major effect on an entity’s financial results, or (2) an acquired business that is classified as held for sale on the date of acquisition. A strategic shift could include a disposal of (1) a separate major line of business, (2) a separate major geographic area of operations, (3) a major equity method investment, or (4) other major parts of an entity.
	We record sales of real estate that do not meet the definition of a discontinued operation in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations.
Revenue and real estate sales gain recognition	Revenue and Real Estate Sales Gain Recognition
	Rental income related to leases is recognized on an accrual basis when due from residents and tenants in accordance with GAAP. Rental payments are generally due on a monthly basis and recognized when earned. The Company recognizes interest income, management and other fees and incentives when earned, and the amounts are fixed and determinable.
	For sale transactions meeting the requirements for full accrual profit recognition, we remove the related assets and liabilities from our Consolidated Balance Sheets and record the gain or loss in the period the transaction closes. For sale transactions that do not meet the full accrual sale criteria due to our continuing involvement, we evaluate the nature of the continuing involvement and account for the transaction under an alternate method of accounting. Unless certain limited criteria are met, non-monetary transactions, including property exchanges, are accounted for at fair value.
	Sales to entities in which we retain or otherwise own an interest are accounted for as partial sales. If all other requirements for recognizing profit under the full accrual method have been satisfied and no other forms of continuing involvement are present, we recognize profit proportionate to the outside interest in the buyer and defer the gain on the interest we retain. The Company recognizes any deferred gain when the property is sold to a third party. In transactions accounted for by us as partial sales, we determine if the buyer of the majority equity interest in the venture was provided a preference as to cash flows in either an operating or a capital waterfall. If a cash flow preference has been provided, we recognize profit only to the extent that proceeds from the sale of the majority equity interest exceed costs related to the entire propert
Income Taxes	Income Taxes
	Due to the structure of the Company as a REIT and the nature of the operations for the operating properties, no provision for federal income taxes has been provided for at UDR. Historically, the Company has generally incurred only state and local excise and franchise taxes. UDR has elected for certain consolidated subsidiaries to be treated as taxable REIT subsidiaries (“TRS”), primarily those engaged in development activities.
	Income taxes for our TRS are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rate is recognized in earnings in the period of the enactment date. The Company’s deferred tax assets are generally the result of differing depreciable lives on capitalized assets and timing of expense recognition for certain accrued liabilities. As of March 31, 2015, UDR’s net deferred tax asset was $7.6 million (net of a valuation allowance of less than $0.1 million), which is included in Other assets on the Consolidated Balance Sheets.
	GAAP defines a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. GAAP also provides guidance on derecognition, classification, interest and penalties, accounting for interim periods, disclosure and transition.
	The Company recognizes its tax positions and evaluates them using a two-step process. First, UDR determines whether a tax position is more likely than not (greater than 50 percent probability) to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Second, the Company will determine the amount of benefit to recognize and record the amount that is more likely than not to be realized upon ultimate settlement.
	UDR had no material unrecognized tax benefit, accrued interest or penalties at March 31, 2015. UDR and its subsidiaries are subject to federal income tax as well as income tax of various state and local jurisdictions. The tax years 2010 through 2013 remain open to examination by tax jurisdictions to which we are subject. When applicable, UDR recognizes interest and/or penalties related to uncertain tax positions in Tax benefit/(expense), net on the Consolidated Statements of Operations.
Policy Loans Receivable, Policy [Policy Text Block]	Notes Receivable

	The following table summarizes our notes receivable, net as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Interest rate at		Balance outstanding
		March 31,		March 31,		December 31, 2014
		2015		2015
	Note due February 2017 (a)	10	%	$	12,994	$	11,869

	Note due July 2017 (b)	8	%	2,500		2,500

	Total notes receivable, net			$	15,494	$	14,369

	(a) The Company has a secured note receivable with an unaffiliated third party with an aggregate commitment of $13.0 million. During the three months ended March 31, 2015, the Company loaned an additional $1.1 million. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) the fifth anniversary of the date of the note (February 2017).
	(b) The Company has a secured note receivable with an unaffiliated third party with an aggregate commitment of $2.5 million. Interest payments are due monthly. The note matures at the earliest of the following: (a) the closing of any private or public capital raising in the amount of $5.0 million or greater; (b) an acquisition; (c) acceleration in the event of default; or (d) the fifth anniversary of the date of the note (July 2017).
	The Company recognized $0.4 million and $1.2 million of interest income from notes receivable during the three months ended March 31, 2015 and 2014, respectively, none of which was related party interest income. Interest income is included in Interest and other income/(expense), net on the Consolidated Statements of Operations.

Significant_Accounting_Policie3

Significant Accounting Policies (UNITED DOMINION REALTY, L.P.) (Policies)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The standard specifically excludes lease contracts. The ASU allows for the use of either the full or modified retrospective transition method, and the standard will be effective for the Company on January 1, 2017; early adoption is not permitted. The Company has not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on our consolidated financial statements and related disclosures.
	Discontinued Operations
	In accordance with GAAP, a discontinued operation represents (1) a component of an entity or group of components that has been disposed of or is classified as held for sale in a single transaction and represents a strategic shift that has or will have a major effect on an entity’s financial results, or (2) an acquired business that is classified as held for sale on the date of acquisition. A strategic shift could include a disposal of (1) a separate major line of business, (2) a separate major geographic area of operations, (3) a major equity method investment, or (4) other major parts of an entity.
	We record sales of real estate that do not meet the definition of a discontinued operation in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations.
Revenue and real estate sales gain recognition	Revenue and Real Estate Sales Gain Recognition
	Rental income related to leases is recognized on an accrual basis when due from residents and tenants in accordance with GAAP. Rental payments are generally due on a monthly basis and recognized when earned. The Company recognizes interest income, management and other fees and incentives when earned, and the amounts are fixed and determinable.
	For sale transactions meeting the requirements for full accrual profit recognition, we remove the related assets and liabilities from our Consolidated Balance Sheets and record the gain or loss in the period the transaction closes. For sale transactions that do not meet the full accrual sale criteria due to our continuing involvement, we evaluate the nature of the continuing involvement and account for the transaction under an alternate method of accounting. Unless certain limited criteria are met, non-monetary transactions, including property exchanges, are accounted for at fair value.
	Sales to entities in which we retain or otherwise own an interest are accounted for as partial sales. If all other requirements for recognizing profit under the full accrual method have been satisfied and no other forms of continuing involvement are present, we recognize profit proportionate to the outside interest in the buyer and defer the gain on the interest we retain. The Company recognizes any deferred gain when the property is sold to a third party. In transactions accounted for by us as partial sales, we determine if the buyer of the majority equity interest in the venture was provided a preference as to cash flows in either an operating or a capital waterfall. If a cash flow preference has been provided, we recognize profit only to the extent that proceeds from the sale of the majority equity interest exceed costs related to the entire propert
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income/(Loss)
Comprehensive Income, Policy [Policy Text Block]	Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to stockholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three months ended March 31, 2015 and 2014, the Company’s other comprehensive income/(loss) consisted of the gain/(loss) (effective portion) on derivative instruments that are designated as and qualify as cash flow hedges, (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) into earnings, and the allocation of other comprehensive income/(loss) to redeemable noncontrolling interests. The (gain)/loss on derivative instruments reclassified from other comprehensive income/(loss) is included in Interest expense on the Consolidated Statements of Operations. See Note 10, Derivatives and Hedging Activity, for further discussion. The allocation of other comprehensive income/(loss) to redeemable noncontrolling interests was $(225,000) and $56,000 during the three months ended March 31, 2015 and 2014, respectively.
Income taxes	Income Taxes
	Due to the structure of the Company as a REIT and the nature of the operations for the operating properties, no provision for federal income taxes has been provided for at UDR. Historically, the Company has generally incurred only state and local excise and franchise taxes. UDR has elected for certain consolidated subsidiaries to be treated as taxable REIT subsidiaries (“TRS”), primarily those engaged in development activities.
	Income taxes for our TRS are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities from a change in tax rate is recognized in earnings in the period of the enactment date. The Company’s deferred tax assets are generally the result of differing depreciable lives on capitalized assets and timing of expense recognition for certain accrued liabilities. As of March 31, 2015, UDR’s net deferred tax asset was $7.6 million (net of a valuation allowance of less than $0.1 million), which is included in Other assets on the Consolidated Balance Sheets.
	GAAP defines a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. GAAP also provides guidance on derecognition, classification, interest and penalties, accounting for interim periods, disclosure and transition.
	The Company recognizes its tax positions and evaluates them using a two-step process. First, UDR determines whether a tax position is more likely than not (greater than 50 percent probability) to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. Second, the Company will determine the amount of benefit to recognize and record the amount that is more likely than not to be realized upon ultimate settlement.
	UDR had no material unrecognized tax benefit, accrued interest or penalties at March 31, 2015. UDR and its subsidiaries are subject to federal income tax as well as income tax of various state and local jurisdictions. The tax years 2010 through 2013 remain open to examination by tax jurisdictions to which we are subject. When applicable, UDR recognizes interest and/or penalties related to uncertain tax positions in Tax benefit/(expense), net on the Consolidated Statements of Operations.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers. The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The standard specifically excludes lease contracts. The ASU allows for the use of either the full or modified retrospective transition method, and the standard will be effective for the Operating Partnership on January 1, 2017; early adoption is not permitted. The Operating Partnership has not yet selected a transition method and we are currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures.
	Discontinued Operations
	In accordance with GAAP, a discontinued operation represents (1) a component of an entity or group of components that has been disposed of or is classified as held for sale in a single transaction and represents a strategic shift that has or will have a major effect on an entity’s financial results, or (2) an acquired business that is classified as held for sale on the date of acquisition. A strategic shift could include a disposal of (1) a separate major line of business, (2) a separate major geographic area of operations, (3) a major equity method investment, or (4) other major parts of an entity.
	We record sales of real estate that do not meet the definition of a discontinued operation in Gain/(loss) on sale of real estate owned, net of tax on the Consolidated Statements of Operations.
Earnings Per Share, Policy [Policy Text Block]	Income/(Loss) Per Operating Partnership Unit
Earnings Per Share, Policy [Policy Text Block]	Basic income/(loss) per OP Unit is computed by dividing net income/(loss) attributable to general and limited partner unitholders by the weighted average number of general and limited partner units outstanding during the year. Diluted income/(loss) per OP Unit reflects the potential dilution that could occur if securities or other contracts to issue OP Units were exercised or converted into OP Units or resulted in the issuance of OP Units and then shared in the income/(loss) of the Operating Partnership.
Revenue and real estate sales gain recognition	Revenue and Real Estate Sales Gain Recognition
	Rental income related to leases is recognized on an accrual basis when due from residents and tenants in accordance with GAAP. Rental payments are generally due on a monthly basis and recognized when earned. The Operating Partnership recognizes interest income, fees and incentives when earned, fixed and determinable.
	For sale transactions meeting the requirements for full accrual profit recognition, we remove the related assets and liabilities from our Consolidated Balance Sheets and record the gain or loss in the period the transaction closes. For sale transactions that do not meet the full accrual sale criteria due to our continuing involvement, we evaluate the nature of the continuing involvement and account for the transaction under an alternate method of accounting. Unless certain limited criteria are met, non-monetary transactions, including property exchanges, are accounted for at fair value.
	Sales to entities in which we or our General Partner retain or otherwise own an interest are accounted for as partial sales. If all other requirements for recognizing profit under the full accrual method have been satisfied and no other forms of continuing involvement are present, we recognize profit proportionate to the outside interest in the buyer and defer the gain on the interest we or our General Partner retain. The Operating Partnership recognizes any deferred gain when the property is sold to a third party. In transactions accounted by us as partial sales, we determine if the buyer of the majority equity interest in the venture was provided a preference as to cash flows in either an operating or a capital waterfall. If a cash flow preference has been provided, we recognize profit only to the extent that proceeds from the sale of the majority equity interest exceed costs related to the entire property.
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income/(Loss)
Comprehensive Income, Policy [Policy Text Block]	Comprehensive income/(loss), which is defined as the change in equity during each period from transactions and other events and circumstances from nonowner sources, including all changes in equity during a period except for those resulting from investments by or distributions to unitholders, is displayed in the accompanying Consolidated Statements of Comprehensive Income/(Loss). For the three months ended March 31, 2015 and 2014, the Operating Partnership’s other comprehensive income/(loss) consisted of the gain/(loss) (effective portion) on derivative instruments that are designated as and qualify as cash flow hedges and (gain)/loss reclassified from other comprehensive income/(loss) into earnings. The (gain)/loss reclassified from other comprehensive income/(loss) is included in Interest expense on the Consolidated Statements of Operations. See Note 7, Derivatives and Hedging Activity, for further discussion.
Income taxes	Income Taxes
	The taxable income or loss of the Operating Partnership is reported on the tax returns of the partners. Accordingly, no provision has been made in the accompanying financial statements for federal or state income taxes on income that is passed through to the partners. However, any state or local revenue, excise or franchise taxes that result from the operating activities of the Operating Partnership are recorded at the entity level. The Operating Partnership’s tax returns are subject to examination by federal and state taxing authorities. Net income for financial reporting purposes differs from the net income for income tax reporting purposes primarily due to temporary differences, principally real estate depreciation and the tax deferral of certain gains on property sales. The differences in depreciation result from differences in the book and tax basis of certain real estate assets and the differences in the methods of depreciation and lives of the real estate assets.
	The Operating Partnership evaluates the accounting and disclosure of tax positions taken or expected to be taken in the course of preparing the Operating Partnership’s tax returns to determine whether the tax positions are “more-likely-than-not” of being sustained by the applicable tax authority. Tax positions not deemed to meet the more-likely-than-not threshold would be recorded as a tax benefit or expense in the current year. Management of the Operating Partnership is required to analyze all open tax years, as defined by the statute of limitations, for all major jurisdictions, which include federal and certain states. The Operating Partnership has no examinations in progress and none are expected at this time.
	Management of the Operating Partnership has reviewed all open tax years (2010 through 2013) of tax jurisdictions and concluded there is no tax liability resulting from unrecognized tax benefits relating to uncertain income tax positions taken or expected to be taken in future tax returns.

Significant_Accounting_Policie4

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Notes receivable	The following table summarizes our notes receivable, net as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Interest rate at		Balance outstanding
		March 31,		March 31,		December 31, 2014
		2015		2015
	Note due February 2017 (a)	10	%	$	12,994	$	11,869

	Note due July 2017 (b)	8	%	2,500		2,500

	Total notes receivable, net			$	15,494	$	14,369

Real_Estate_Owned_Tables

Real Estate Owned (Tables)	3 Months Ended
	Mar. 31, 2015
Real Estate [Abstract]
Summary of carrying amounts for real estate owned (at cost)	The following table summarizes the carrying amounts for our real estate owned (at cost) as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Land and land improvements	$	1,984,019		$	1,980,221

	Depreciable property — held and used:
	Building, improvements, and furniture, fixtures and equipment	6,272,976			6,225,406

	Under development:
	Land and land improvements	24,584			24,584

	Building, improvements, and furniture, fixtures and equipment	172,069			153,048

	Real estate owned	8,453,648			8,383,259

	Accumulated depreciation	(2,522,100		)	(2,434,772		)
	Real estate owned, net	$	5,931,548		$	5,948,487

Real_Estate_Owned_UNITED_DOMIN1

Real Estate Owned (UNITED DOMINION REALTY, L.P.) (Tables)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
Summary of carrying amounts for real estate owned (at cost)	The following table summarizes the carrying amounts for our real estate owned (at cost) as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Land and land improvements	$	1,984,019		$	1,980,221

	Depreciable property — held and used:
	Building, improvements, and furniture, fixtures and equipment	6,272,976			6,225,406

	Under development:
	Land and land improvements	24,584			24,584

	Building, improvements, and furniture, fixtures and equipment	172,069			153,048

	Real estate owned	8,453,648			8,383,259

	Accumulated depreciation	(2,522,100		)	(2,434,772		)
	Real estate owned, net	$	5,931,548		$	5,948,487

United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Summary of carrying amounts for real estate owned (at cost)	The following table summarizes the carrying amounts for our real estate owned (at cost) as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Land	$	1,008,358		$	1,008,014

	Depreciable property — held and used:
	Buildings, improvements, and furniture, fixture and equipment	3,240,437			3,230,756

	Real estate owned	4,248,795			4,238,770

	Accumulated depreciation	(1,447,513		)	(1,403,303		)
	Real estate owned, net	$	2,801,282		$	2,835,467

Discontinued_Operations_Tables

Discontinued Operations (Tables)	3 Months Ended
	Mar. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Summary of income from discontinued operations	The following is a summary of income/(loss) from discontinued operations, net of tax for the three months ended March 31, 2015 and 2014 (dollars in thousands):


		Three Months Ended
		March 31,
		2015		2014
	Rental income	$	—	$	48

	Rental expenses	—		125

	Property management	—		1

	Interest and other (income)/expense, net	—		9

	Income/(loss) from discontinued operations, net of tax	$	—	$	(87	)


	Income/(loss) from discontinued operations attributable to UDR, Inc.	$	—	$	(84	)

Joint_Ventures_Tables

Joint Ventures (Tables)	3 Months Ended
Joint Ventures (Tables)	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Combined Summary of Balance Sheets Relating to Unconsolidated Joint Ventures [Table Text Block]	We evaluate our investments in unconsolidated joint ventures and partnerships when events or changes in circumstances indicate that there may be an other-than-temporary decline in value. We consider various factors to determine if a decrease in the value of the investment is other-than-temporary. The Company did not recognize any other-than-temporary decreases in the value of its investments in unconsolidated joint ventures or partnerships during the three months ended March 31, 2015 and 2014.

	Combined summary balance sheets relating to all of the unconsolidated joint ventures and partnerships (not just our proportionate share) are presented below as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,				December 31, 2014
		2015				December 31, 2014
	Total real estate, net	$	2,970,102			$	2,941,803
	Total real estate, net	$	2,970,102			$	2,941,803
	Assets held for sale	—				216,196
	Assets held for sale	—				216,196
	Cash and cash equivalents	29,544				32,544
	Cash and cash equivalents	29,544				32,544
	Other assets	31,162				28,707
	Other assets	31,162				28,707
	Total assets	$	3,030,808			$	3,219,250
	Total assets	$	3,030,808			$	3,219,250

	Amount due to UDR	$	4,691			$	2,997
	Amount due to UDR	$	4,691			$	2,997
	Third party debt	1,514,886				1,504,477
	Third party debt	1,514,886				1,504,477
	Liabilities held for sale	—				229,706
	Liabilities held for sale	—				229,706
	Accounts payable and accrued liabilities	52,146				44,335
	Accounts payable and accrued liabilities	52,146				44,335
	Total liabilities	1,571,723				1,781,515
	Total liabilities	1,571,723				1,781,515
	Total equity	1,459,085				1,437,735
	Total equity	1,459,085				1,437,735
	Total liabilities and equity	$	3,030,808			$	3,219,250
	Total liabilities and equity	$	3,030,808			$	3,219,250

	UDR’s investment in unconsolidated joint ventures	$	763,540			$	718,226
	UDR’s investment in unconsolidated joint ventures	$	763,540			$	718,226
Schedule of Equity Method Investments [Table Text Block]	The following table summarizes the Company’s investment in and advances to unconsolidated joint ventures and partnerships, net, which are accounted for under the equity method of accounting as of March 31, 2015 and December 31, 2014 (dollars in thousands):


	Joint Venture		Location of Properties		Number of Properties		Number of Apartment Homes		Investment at					UDR’s Ownership Interest
					March 31,		March 31,		March 31,		December 31,			March 31,			December 31,
					2015		2015		2015		2014			2015			2014
	Operating and development:
	UDR/MetLife I		Various		4 land parcels		—		$	13,473	$	13,306		15.7		%	15.7		%
	UDR/MetLife I		Various		4 land parcels		—		$	13,473	$	13,306		15.7		%	15.7		%
	UDR/MetLife II		Various		21 operating communities		4,642		429,635		431,277			50		%	50		%
	UDR/MetLife II		Various		21 operating communities		4,642		429,635		431,277			50		%	50		%
	Other UDR/MetLife Development Joint Ventures				1 operating community;
					4 development communities (a);
			Various		1 land parcels		1,437		145,681		134,939			50.6		%	50.6		%
			Various		1 land parcels		1,437		145,681		134,939			50.6		%	50.6		%
	UDR/MetLife Vitruvian Park®		Addison, TX		3 operating communities
					6 land parcels		1,130		78,669		80,302			50		%	50		%
					6 land parcels		1,130		78,669		80,302			50		%	50		%
	UDR/KFH		Washington, D.C.		3 operating communities		660		20,435		21,596			30		%	30		%
	UDR/KFH		Washington, D.C.		3 operating communities		660		20,435		21,596			30		%	30		%
	Texas (b)		Texas		—		—		—		(25,901		)	—		%	20		%
	Texas (b)		Texas		—		—		—		(25,901		)	—		%	20		%
	Investment in and advances to unconsolidated joint ventures, net, before participating loan investment								687,893		655,519
									687,893		655,519

			Location		Interest Rate		Years To Maturity		Investment at					Income From Participating Loan Investment for the Three Months Ended March 31,
									March 31,		December 31,			2015			2014
									2015		2014			2015			2014
	Participating loan investment:
	Steele Creek		Denver, CO		6.50%		2.3		75,647		62,707			$	1,154		$	321
	Steele Creek		Denver, CO		6.50%		2.3		75,647		62,707			$	1,154		$	321

	Total investment in and advances to unconsolidated joint ventures, net								$	763,540	$	718,226
									$	763,540	$	718,226

	(a)	The number of apartment homes for the communities under development presented in the table above is based on the projected number of total homes. As of March 31, 2015, no apartment homes had been completed in Other UDR/MetLife Development Joint Ventures.
	(b) In January 2015, the eight communities held by the Texas joint venture were sold, generating net proceeds to UDR of $43.5 million. The Company recorded promote and disposition fee income of $9.6 million and a gain of $59.1 million (including $24.2 million of previously deferred gains) in connection with the sale.
Financial information relating to unconsolidated joint ventures operations	Combined summary financial information relating to all of the unconsolidated joint ventures’ and partnerships’ operations (not just our proportionate share), is presented below for the three months ended March 31, 2015 and 2014 (dollars in thousands):


		Three Months Ended
		March 31,
		2015				2014
	Total revenues	$	54,546			$	38,955
	Total revenues	$	54,546			$	38,955
	Property operating expenses	(20,168		)		(14,360		)
	Real estate depreciation and amortization	(19,351		)		(14,688		)
	Operating income/(loss)	15,027				9,907
	Operating income/(loss)	15,027				9,907
	Interest expense	(16,061		)		(12,151		)
	Income/(loss) from discontinued operations	182,488				(29,997		)
	Income/(loss) from discontinued operations	182,488				(29,997		)
	Net income/(loss)	$	181,454			$	(32,241	)
	Net income/(loss)	$	181,454			$	(32,241	)
	UDR income/(loss) from unconsolidated entities	$	59,159			$	(3,565	)
	UDR income/(loss) from unconsolidated entities	$	59,159			$	(3,565	)
Combined summary of balance sheets relating to unconsolidated joint ventures	JOINT VENTURES AND PARTNERSHIPS
	UDR has entered into joint ventures and partnerships with unrelated third parties to acquire real estate assets that are either consolidated and included in Real estate owned on the Consolidated Balance Sheets or are accounted for under the equity method of accounting, and are included in Investment in and advances to unconsolidated joint ventures, net on the Consolidated Balance Sheets. The Company consolidates the entities that we control as well as any variable interest entity where we are the primary beneficiary. In addition, the Company consolidates any joint venture or partnership in which we are the general partner or managing member and the third party does not have the ability to substantively participate in the decision-making process nor the ability to remove us as general partner or managing member without cause.

	UDR’s joint ventures and partnerships are funded with a combination of debt and equity. Our losses are limited to our investment and except as noted below, the Company does not guarantee any debt, capital payout or other obligations associated with our joint ventures and partnerships.
	Unconsolidated Joint Ventures and Partnerships
	The Company recognizes earnings or losses from our investments in unconsolidated joint ventures and partnerships consisting of our proportionate share of the net earnings or losses of the joint ventures and partnerships. In addition, we may earn fees for providing management services to the unconsolidated joint ventures and partnerships.
	The following table summarizes the Company’s investment in and advances to unconsolidated joint ventures and partnerships, net, which are accounted for under the equity method of accounting as of March 31, 2015 and December 31, 2014 (dollars in thousands):


	Joint Venture		Location of Properties		Number of Properties		Number of Apartment Homes		Investment at					UDR’s Ownership Interest
					March 31,		March 31,		March 31,		December 31,			March 31,			December 31,
					2015		2015		2015		2014			2015			2014
	Operating and development:
	UDR/MetLife I		Various		4 land parcels		—		$	13,473	$	13,306		15.7		%	15.7		%
	UDR/MetLife I		Various		4 land parcels		—		$	13,473	$	13,306		15.7		%	15.7		%
	UDR/MetLife II		Various		21 operating communities		4,642		429,635		431,277			50		%	50		%
	UDR/MetLife II		Various		21 operating communities		4,642		429,635		431,277			50		%	50		%
	Other UDR/MetLife Development Joint Ventures				1 operating community;
					4 development communities (a);
			Various		1 land parcels		1,437		145,681		134,939			50.6		%	50.6		%
			Various		1 land parcels		1,437		145,681		134,939			50.6		%	50.6		%
	UDR/MetLife Vitruvian Park®		Addison, TX		3 operating communities
					6 land parcels		1,130		78,669		80,302			50		%	50		%
					6 land parcels		1,130		78,669		80,302			50		%	50		%
	UDR/KFH		Washington, D.C.		3 operating communities		660		20,435		21,596			30		%	30		%
	UDR/KFH		Washington, D.C.		3 operating communities		660		20,435		21,596			30		%	30		%
	Texas (b)		Texas		—		—		—		(25,901		)	—		%	20		%
	Texas (b)		Texas		—		—		—		(25,901		)	—		%	20		%
	Investment in and advances to unconsolidated joint ventures, net, before participating loan investment								687,893		655,519
									687,893		655,519

			Location		Interest Rate		Years To Maturity		Investment at					Income From Participating Loan Investment for the Three Months Ended March 31,
									March 31,		December 31,			2015			2014
									2015		2014			2015			2014
	Participating loan investment:
	Steele Creek		Denver, CO		6.50%		2.3		75,647		62,707			$	1,154		$	321
	Steele Creek		Denver, CO		6.50%		2.3		75,647		62,707			$	1,154		$	321

	Total investment in and advances to unconsolidated joint ventures, net								$	763,540	$	718,226
									$	763,540	$	718,226

	(a)	The number of apartment homes for the communities under development presented in the table above is based on the projected number of total homes. As of March 31, 2015, no apartment homes had been completed in Other UDR/MetLife Development Joint Ventures.
	(b) In January 2015, the eight communities held by the Texas joint venture were sold, generating net proceeds to UDR of $43.5 million. The Company recorded promote and disposition fee income of $9.6 million and a gain of $59.1 million (including $24.2 million of previously deferred gains) in connection with the sale.
	Subsequent to quarter end, the Company entered into a joint venture agreement with real estate private equity firm, The Wolff Company (“Wolff”), to invest $136 million for a 48 percent interest in a portfolio of five communities that are currently under construction. The transaction is expected to close in May 2015. The communities are located in three of the Company’s core, coastal markets: Metro Seattle, Los Angeles and Orange County, CA. UDR will earn a 6.5 percent preferred return on its $136 million investment through each individual community’s date of stabilization, defined as when a community reaches 80 percent occupancy for ninety consecutive days, while Wolff is allocated all income and expense during the pre-stabilization period. Upon stabilization, income and expense will be shared based on each partner’s ownership percentage. The Company will serve as property manager and be paid a management fee during the lease-up phase and subsequent operation of each of the communities.

	The Company has a fixed price option to acquire Wolff’s remaining interest in each community beginning one year after completion. If the options are exercised for all five communities, the Company’s total price will be $597 million. In the event the Company does not exercise its options to purchase at least two communities, Wolff will be entitled to a 6.5 percent return on its implied equity in the communities not acquired. Wolff is providing certain guaranties and there will be construction loans on all five communities. Once completed the five communities will contain 1,533 homes.
	As of March 31, 2015 and December 31, 2014, the Company had deferred fees and deferred profit from the sale of properties to joint ventures or partnerships of $5.6 million and $28.5 million, respectively, which will be recognized through earnings over the weighted average life of the related properties, upon the disposition of the properties to a third party, or upon completion of certain development obligations.
	The Company recognized management fees for our management of the joint ventures and partnerships of $2.6 million and $3.3 million for the three months ended March 31, 2015 and 2014, respectively. The management fees are included in Joint venture management and other fees on the Consolidated Statements of Operations.
	The Company may, in the future, make additional capital contributions to certain of our joint ventures and partnerships should additional capital contributions be necessary to fund acquisitions or operations.
	We evaluate our investments in unconsolidated joint ventures and partnerships when events or changes in circumstances indicate that there may be an other-than-temporary decline in value. We consider various factors to determine if a decrease in the value of the investment is other-than-temporary. The Company did not recognize any other-than-temporary decreases in the value of its investments in unconsolidated joint ventures or partnerships during the three months ended March 31, 2015 and 2014.

	Combined summary balance sheets relating to all of the unconsolidated joint ventures and partnerships (not just our proportionate share) are presented below as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,				December 31, 2014
		2015				December 31, 2014
	Total real estate, net	$	2,970,102			$	2,941,803
	Total real estate, net	$	2,970,102			$	2,941,803
	Assets held for sale	—				216,196
	Assets held for sale	—				216,196
	Cash and cash equivalents	29,544				32,544
	Cash and cash equivalents	29,544				32,544
	Other assets	31,162				28,707
	Other assets	31,162				28,707
Total assets	$	3,030,808			$	3,219,250
Total assets	$	3,030,808			$	3,219,250

Amount due to UDR	$	4,691			$	2,997
Amount due to UDR	$	4,691			$	2,997
Third party debt	1,514,886				1,504,477
Third party debt	1,514,886				1,504,477
Liabilities held for sale	—				229,706
Liabilities held for sale	—				229,706
Accounts payable and accrued liabilities	52,146				44,335
Accounts payable and accrued liabilities	52,146				44,335
Total liabilities	1,571,723				1,781,515
Total liabilities	1,571,723				1,781,515
Total equity	1,459,085				1,437,735
Total equity	1,459,085				1,437,735
Total liabilities and equity	$	3,030,808			$	3,219,250
Total liabilities and equity	$	3,030,808			$	3,219,250

UDR’s investment in unconsolidated joint ventures	$	763,540			$	718,226
UDR’s investment in unconsolidated joint ventures	$	763,540			$	718,226
Combined summary financial information relating to all of the unconsolidated joint ventures’ and partnerships’ operations (not just our proportionate share), is presented below for the three months ended March 31, 2015 and 2014 (dollars in thousands):


	Three Months Ended
	March 31,
	2015				2014
Total revenues	$	54,546			$	38,955
Total revenues	$	54,546			$	38,955
Property operating expenses	(20,168		)		(14,360		)
Real estate depreciation and amortization	(19,351		)		(14,688		)
Operating income/(loss)	15,027				9,907
Operating income/(loss)	15,027				9,907
Interest expense	(16,061		)		(12,151		)
Income/(loss) from discontinued operations	182,488				(29,997		)
Income/(loss) from discontinued operations	182,488				(29,997		)
Net income/(loss)	$	181,454			$	(32,241	)
Net income/(loss)	$	181,454			$	(32,241	)
UDR income/(loss) from unconsolidated entities	$	59,159			$	(3,565	)
UDR income/(loss) from unconsolidated entities	$	59,159			$	(3,565	)

Secured_and_Unsecured_Debt_Tab

Secured and Unsecured Debt (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Secured debt instruments	The following is a summary of our secured and unsecured debt at March 31, 2015 and December 31, 2014 (dollars in thousands):


								Three Months Ended
		Principal Outstanding						31-Mar-15
		March 31,			December 31, 2014			Weighted Average			Weighted Average		Number of Communities
		2015						Interest Rate			Years to Maturity		Encumbered
	Secured Debt:
	Fixed Rate Debt
	Mortgage notes payable (a)	$	411,271		$	401,210		5.49	%		1.4		7

	Fannie Mae credit facilities (b)	567,169			568,086			5.12	%		3.8		22

	Total fixed rate secured debt	978,440			969,296			5.28	%		2.8		29

	Variable Rate Debt

	Mortgage notes payable	31,337			31,337			1.94	%		1.8		1

	Tax-exempt secured notes payable (c)	94,700			94,700			0.76	%		7.9		2

	Fannie Mae credit facilities (b)	266,196			266,196			1.62	%		4.9		7

	Total variable rate secured debt	392,233			392,233			1.44	%		5.4		10

	Total Secured Debt	1,370,673			1,361,529			4.18	%		3.5		39


	Unsecured Debt:
	Commercial Banks
	Borrowings outstanding under an unsecured credit facility due December 2017 (d) (f)	389,000			152,500			1.08	%		2.7

	Senior Unsecured Notes
	5.25% Medium-Term Notes due January 2015 (net of discounts of $0 and $6, respectively) (e)	—			325,169			—	%		—

	5.25% Medium-Term Notes due January 2016	83,260			83,260			5.25	%		0.8

	6.21% Medium-Term Notes due July 2016	12,865			—			6.21	%		1.3

	4.25% Medium-Term Notes due June 2018 (net of discounts of $1,358 and $1,465, respectively) (f)	298,642			298,535			4.25	%		3.2

	1.70% Term Notes due June 2018 (f)	215,000			215,000			1.7	%		3.2

	1.53% Term Notes due June 2018 (f)	100,000			100,000			1.53	%		3.2

	1.32% Term Notes due June 2018 (f)	35,000			35,000			1.32	%		3.2

	3.70% Medium-Term Notes due October 2020 (net of discounts of $44 and $46, respectively) (f)	299,956			299,954			3.7	%		5.5

	4.63% Medium-Term Notes due January 2022 (net of discounts of $2,433 and $2,523, respectively) (f)	397,567			397,477			4.63	%		6.8

	3.75% Medium-Term Notes due July 2024 (net of discount of $964 and $990, respectively) (f)	299,036			299,010			3.75	%		9.3

	8.50% Debentures due September 2024	15,644			15,644			8.5	%		9.5

	Other	26			27			N/A			N/A

	Total Unsecured Debt	2,145,996			2,221,576			3.26	%		4.9

	Total Debt	$	3,516,669		$	3,583,105		3.62	%		4.4

Secured credit facilities	Further information related to these credit facilities is as follows (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Borrowings outstanding	$	833,365		$	834,282

	Weighted average borrowings during the period ended	833,697			835,873

	Maximum daily borrowings during the period ended	834,003			837,564

	Weighted average interest rate during the period ended	4		%	4.1		%
	Weighted average interest rate at the end of the period	4		%	4		%
Schedule of Maturities of Long-term Debt [Table Text Block]	The aggregate maturities, including amortizing principal payments of unsecured and secured debt, of total debt for the next five calendar years subsequent to March 31, 2015 are as follows (dollars in thousands):


	Year		Total Fixed Secured Debt			Total Variable Secured Debt			Total Secured Debt			Total Unsecured Debt (a)		Total Debt
	2015		$	194,779		$	—		$	194,779		$	114	$	194,893

	2016		148,223			—			148,223			94,468		242,691

	2017		177,882			96,337			274,219			389,000		663,219

	2018		121,685			104,787			226,472			648,444		874,916

	2019		245,871			67,700			313,571			—		313,571

	Thereafter		90,000			123,409			213,409			1,013,970		1,227,379

	Total		$	978,440		$	392,233		$	1,370,673		$	2,145,996	$	3,516,669

Debt_UNITED_DOMINION_REALTY_LP1

Debt (UNITED DOMINION REALTY, L.P.) (Tables)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
Secured debt instruments	The following is a summary of our secured and unsecured debt at March 31, 2015 and December 31, 2014 (dollars in thousands):


								Three Months Ended
		Principal Outstanding						31-Mar-15
		March 31,			December 31, 2014			Weighted Average			Weighted Average		Number of Communities
		2015						Interest Rate			Years to Maturity		Encumbered
	Secured Debt:
	Fixed Rate Debt
	Mortgage notes payable (a)	$	411,271		$	401,210		5.49	%		1.4		7

	Fannie Mae credit facilities (b)	567,169			568,086			5.12	%		3.8		22

	Total fixed rate secured debt	978,440			969,296			5.28	%		2.8		29

	Variable Rate Debt

	Mortgage notes payable	31,337			31,337			1.94	%		1.8		1

	Tax-exempt secured notes payable (c)	94,700			94,700			0.76	%		7.9		2

	Fannie Mae credit facilities (b)	266,196			266,196			1.62	%		4.9		7

	Total variable rate secured debt	392,233			392,233			1.44	%		5.4		10

	Total Secured Debt	1,370,673			1,361,529			4.18	%		3.5		39


	Unsecured Debt:
	Commercial Banks
	Borrowings outstanding under an unsecured credit facility due December 2017 (d) (f)	389,000			152,500			1.08	%		2.7

	Senior Unsecured Notes
	5.25% Medium-Term Notes due January 2015 (net of discounts of $0 and $6, respectively) (e)	—			325,169			—	%		—

	5.25% Medium-Term Notes due January 2016	83,260			83,260			5.25	%		0.8

	6.21% Medium-Term Notes due July 2016	12,865			—			6.21	%		1.3

	4.25% Medium-Term Notes due June 2018 (net of discounts of $1,358 and $1,465, respectively) (f)	298,642			298,535			4.25	%		3.2

	1.70% Term Notes due June 2018 (f)	215,000			215,000			1.7	%		3.2

	1.53% Term Notes due June 2018 (f)	100,000			100,000			1.53	%		3.2

	1.32% Term Notes due June 2018 (f)	35,000			35,000			1.32	%		3.2

	3.70% Medium-Term Notes due October 2020 (net of discounts of $44 and $46, respectively) (f)	299,956			299,954			3.7	%		5.5

	4.63% Medium-Term Notes due January 2022 (net of discounts of $2,433 and $2,523, respectively) (f)	397,567			397,477			4.63	%		6.8

	3.75% Medium-Term Notes due July 2024 (net of discount of $964 and $990, respectively) (f)	299,036			299,010			3.75	%		9.3

	8.50% Debentures due September 2024	15,644			15,644			8.5	%		9.5

	Other	26			27			N/A			N/A

	Total Unsecured Debt	2,145,996			2,221,576			3.26	%		4.9

	Total Debt	$	3,516,669		$	3,583,105		3.62	%		4.4

Secured credit facilities	Further information related to these credit facilities is as follows (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Borrowings outstanding	$	833,365		$	834,282

	Weighted average borrowings during the period ended	833,697			835,873

	Maximum daily borrowings during the period ended	834,003			837,564

	Weighted average interest rate during the period ended	4		%	4.1		%
	Weighted average interest rate at the end of the period	4		%	4		%
Aggregate maturities of secured debt	The aggregate maturities, including amortizing principal payments of unsecured and secured debt, of total debt for the next five calendar years subsequent to March 31, 2015 are as follows (dollars in thousands):


	Year		Total Fixed Secured Debt			Total Variable Secured Debt			Total Secured Debt			Total Unsecured Debt (a)		Total Debt
	2015		$	194,779		$	—		$	194,779		$	114	$	194,893

	2016		148,223			—			148,223			94,468		242,691

	2017		177,882			96,337			274,219			389,000		663,219

	2018		121,685			104,787			226,472			648,444		874,916

	2019		245,871			67,700			313,571			—		313,571

	Thereafter		90,000			123,409			213,409			1,013,970		1,227,379

	Total		$	978,440		$	392,233		$	1,370,673		$	2,145,996	$	3,516,669

United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Secured debt instruments	Secured debt consists of the following as of March 31, 2015 and December 31, 2014 (dollars in thousands):


								Three Months Ended
		Principal Outstanding						31-Mar-15
		March 31,			December 31, 2014			Weighted Average			Weighted Average	Number of Communities
		2015						Interest Rate			Years to Maturity	Encumbered
	Fixed Rate Debt
	Mortgage notes payable	$	376,207		$	378,371		5.48	%		1.4	5

	Fannie Mae credit facilities	333,735			333,828			4.9	%		4.3	10

	Total fixed rate secured debt	709,942			712,199			5.21	%		2.8	15

	Variable Rate Debt
	Tax-exempt secured note payable	27,000			27,000			0.77	%		17	1

	Fannie Mae credit facilities	192,760			192,760			1.85	%		5.7	5

	Total variable rate secured debt	219,760			219,760			1.72	%		7.1	6

	Total Secured Debt	$	929,702		$	931,959		4.38	%		3.8	21

Secured credit facilities	The following information relates to the credit facilities allocated to the Operating Partnership (dollars in thousands):


		March 31,			December 31, 2014
		2015
	Borrowings outstanding	$	526,495		$	526,588

	Weighted average borrowings during the period ended	526,705			527,592

	Maximum daily borrowings during the period	526,898			528,659

	Weighted average interest rate during the period ended	4		%	4.1		%
	Interest rate at the end of the period	4		%	4		%
Aggregate maturities of secured debt	The aggregate maturities of the Operating Partnership’s secured debt due during each of the next five calendar years subsequent to March 31, 2015 are as follows (dollars in thousands):


			Fixed						Variable
	Year		Mortgage			Secured Credit			Tax-Exempt			Secured Credit		Total
			Notes Payable			Facilities			Secured Notes Payable			Facilities
	2015		$	190,582		$	274		$	—		$	—	$	190,856

	2016		131,021			385			—			—		131,406

	2017		913			15,640			—			6,566		23,119

	2018		968			111,052			—			96,974		208,994

	2019		52,723			123,095			—			—		175,818

	Thereafter		—			83,289			27,000			89,220		199,509

	Total		$	376,207		$	333,735		$	27,000		$	192,760	$	929,702

IncomeLoss_Per_Share_Tables

Income/(Loss) Per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	The following table sets forth the additional shares of common stock outstanding by equity instrument if converted to common stock for each of the three months ended March 31, 2015 and 2014 (shares in thousands):


		Three Months Ended
		March 31,
		2015			2014
	OP Units	9,165			9,319

	Preferred stock	3,036			3,036

	Stock options and unvested restricted stock	1,828			1,645

(Loss)/earnings per share	The following table sets forth the computation of basic and diluted income/(loss) per share for the periods presented (dollars and shares in thousands, except per share data):


		Three Months Ended
		March 31,
		2015				2014
	Numerator for income/(loss) per share:
	Income/(loss) from continuing operations	$	76,417			$	(5,195	)

	Gain/(loss) on sale of real estate owned, net of tax	—				24,294

	(Income)/loss from continuing operations attributable to redeemable noncontrolling interests in the Operating Partnership	(2,588		)		(650		)
	(Income)/loss from continuing operations attributable to noncontrolling interests	(7		)		(4		)
	Income/(loss) from continuing operations attributable to UDR, Inc.	73,822				18,445

	Distributions to preferred stockholders - Series E (Convertible)	(931		)		(931		)
	Income/(loss) from continuing operations attributable to common stockholders	$	72,891			$	17,514


	Income/(loss) from discontinued operations, net of tax	$	—			$	(87	)

	(Income)/loss from discontinued operations attributable to redeemable noncontrolling interests in the Operating Partnership	—				3

	Income/(loss) from discontinued operations attributable to common stockholders	$	—			$	(84	)


	Net income/(loss) attributable to common stockholders	$	72,891			$	17,430


	Denominator for income/(loss) per share:
	Weighted average common shares outstanding	258,100				251,213

	Non-vested restricted stock awards	(1,266		)		(1,036		)
	Denominator for basic income/(loss) per share	256,834				250,177

	Incremental shares issuable from assumed conversion of stock options and unvested restricted stock	1,828				1,645

	Denominator for diluted income/(loss) per share	258,662				251,822


	Income/(loss) per weighted average common share-basic:
	Income/(loss) from continuing operations attributable to common stockholders	$	0.28			$	0.07

	Income/(loss) from discontinued operations attributable to common stockholders	0				0

	Net income/(loss) attributable to common stockholders	$	0.28			$	0.07


	Income/(loss) per weighted average common share-diluted:
	Income/(loss) from continuing operations attributable to common stockholders	$	0.28			$	0.07

	Income/(loss) from discontinued operations attributable to common stockholders	0				0

	Net income/(loss) attributable to common stockholders	$	0.28			$	0.07

Noncontrolling_Interests_Table

Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest [Abstract]
Redeemable noncontrolling interests in the Operating Partnership	The following table sets forth redeemable noncontrolling interests in the Operating Partnership for the following period (dollars in thousands):


	Redeemable noncontrolling interests in the Operating Partnership, December 31, 2014	$	282,480

	Mark-to-market adjustment to redeemable noncontrolling interests in the Operating Partnership	29,696

	Conversion of OP Units to Common Stock	(17		)
	Net income/(loss) attributable to redeemable noncontrolling interests in the Operating Partnership	2,588

	Distributions to redeemable noncontrolling interests in the Operating Partnership	(2,639		)
	Allocation of other comprehensive income/(loss)	(225		)
	Redeemable noncontrolling interests in the Operating Partnership, March 31, 2015	$	311,883


	The following sets forth net income/(loss) attributable to common stockholders and transfers from redeemable noncontrolling interests in the Operating Partnership for the following periods (dollars in thousands):


		Three Months Ended
		March 31,
		2015			2014
	Net income/(loss) attributable to common stockholders	$	72,891		$	17,430

	Conversion of OP Units to UDR Common stock	17			—

	Change in equity from net income/(loss) attributable to common stockholders and conversion of OP Units to UDR Common Stock	$	72,908		$	17,430

Fair_Value_of_Derivatives_and_2

Fair Value of Derivatives and Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Estimated fair values	The estimated fair values of the Company’s financial instruments either recorded or disclosed on a recurring basis as of March 31, 2015 and December 31, 2014 are summarized as follows (dollars in thousands):


								Fair Value at March 31, 2015, Using
		Total Carrying Amount in Statement of Financial Position at March 31, 2015			Fair Value Estimate at March 31, 2015			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	15,494		$	15,923		$	—		$	—		$	15,923

	Derivatives - Interest rate contracts (b)	29			29			—			29			—

	Total assets	$	15,523		$	15,952		$	—		$	29		$	15,923


	Derivatives - Interest rate contracts (b)	$	17,112		$	17,112		$	—		$	17,112		$	—

	Secured debt instruments - fixed rate: (c)
	Mortgage notes payable	411,271			425,969			—			—			425,969

	Fannie Mae credit facilities	567,169			599,580			—			—			599,580

	Secured debt instruments - variable rate: (c)
	Mortgage notes payable	31,337			31,337			—			—			31,337

	Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

	Fannie Mae credit facilities	266,196			266,196			—			—			266,196

	Unsecured debt instruments: (c)
	Commercial bank	389,000			389,000			—			—			389,000

	Senior unsecured notes	1,756,996			1,852,361			—			—			1,852,361

	Total liabilities	$	3,533,781		$	3,676,255		$	—		$	17,112		$	3,659,143


	Redeemable noncontrolling interests in the Operating Partnership (d)	$	311,883		$	311,883		$	—		$	311,883		$	—



								Fair Value at December 31, 2014, Using
		Total Carrying Amount in Statement of Financial Position at December 31, 2014			Fair Value Estimate at December 31, 2014			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	14,369		$	14,808		$	—		$	—		$	14,808

	Derivatives- Interest rate contracts (b)	88			88			—			88			—

	Total assets	$	14,457		$	14,896		$	—		$	88		$	14,808


	Derivatives- Interest rate contracts (b)	$	10,368		$	10,368		$	—		$	10,368		$	—

	Secured debt instruments- fixed rate: (c)
	Mortgage notes payable	401,210			415,663			—			—			415,663

Fannie Mae credit facilities	568,086			606,623			—			—			606,623

Secured debt instruments- variable rate: (c)

Mortgage notes payable	31,337			31,337			—			—			31,337

Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

Fannie Mae credit facilities	266,196			266,196			—			—			266,196

Unsecured debt instruments: (c)
Commercial bank	152,500			152,500			—			—			152,500

Senior unsecured notes	2,069,076			2,144,125			—			—			2,144,125

Total liabilities	$	3,593,473		$	3,721,512		$	—		$	10,368		$	3,711,144


Redeemable noncontrolling interests in the Operating Partnership (d)	$	282,480		$	282,480		$	—		$	282,480		$	—



(a)	See Note 2, Significant Accounting Policies.

(b)	See Note 10, Derivatives and Hedging Activity.

(c)	See Note 6, Secured and Unsecured Debt.

(d)	See Note 8, Noncontrolling Interests.

Fair_Value_of_Derivatives_and_3

Fair Value of Derivatives and Financial Instruments (UNITED DOMINION REALTY, L.P.) (Tables)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
Estimated fair values	The estimated fair values of the Company’s financial instruments either recorded or disclosed on a recurring basis as of March 31, 2015 and December 31, 2014 are summarized as follows (dollars in thousands):


								Fair Value at March 31, 2015, Using
		Total Carrying Amount in Statement of Financial Position at March 31, 2015			Fair Value Estimate at March 31, 2015			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	15,494		$	15,923		$	—		$	—		$	15,923

	Derivatives - Interest rate contracts (b)	29			29			—			29			—

	Total assets	$	15,523		$	15,952		$	—		$	29		$	15,923


	Derivatives - Interest rate contracts (b)	$	17,112		$	17,112		$	—		$	17,112		$	—

	Secured debt instruments - fixed rate: (c)
	Mortgage notes payable	411,271			425,969			—			—			425,969

	Fannie Mae credit facilities	567,169			599,580			—			—			599,580

	Secured debt instruments - variable rate: (c)
	Mortgage notes payable	31,337			31,337			—			—			31,337

	Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

	Fannie Mae credit facilities	266,196			266,196			—			—			266,196

	Unsecured debt instruments: (c)
	Commercial bank	389,000			389,000			—			—			389,000

	Senior unsecured notes	1,756,996			1,852,361			—			—			1,852,361

	Total liabilities	$	3,533,781		$	3,676,255		$	—		$	17,112		$	3,659,143


	Redeemable noncontrolling interests in the Operating Partnership (d)	$	311,883		$	311,883		$	—		$	311,883		$	—



								Fair Value at December 31, 2014, Using
		Total Carrying Amount in Statement of Financial Position at December 31, 2014			Fair Value Estimate at December 31, 2014			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Notes receivable (a)	$	14,369		$	14,808		$	—		$	—		$	14,808

	Derivatives- Interest rate contracts (b)	88			88			—			88			—

	Total assets	$	14,457		$	14,896		$	—		$	88		$	14,808


	Derivatives- Interest rate contracts (b)	$	10,368		$	10,368		$	—		$	10,368		$	—

	Secured debt instruments- fixed rate: (c)
	Mortgage notes payable	401,210			415,663			—			—			415,663

Fannie Mae credit facilities	568,086			606,623			—			—			606,623

Secured debt instruments- variable rate: (c)

Mortgage notes payable	31,337			31,337			—			—			31,337

Tax-exempt secured notes payable	94,700			94,700			—			—			94,700

Fannie Mae credit facilities	266,196			266,196			—			—			266,196

Unsecured debt instruments: (c)
Commercial bank	152,500			152,500			—			—			152,500

Senior unsecured notes	2,069,076			2,144,125			—			—			2,144,125

Total liabilities	$	3,593,473		$	3,721,512		$	—		$	10,368		$	3,711,144


Redeemable noncontrolling interests in the Operating Partnership (d)	$	282,480		$	282,480		$	—		$	282,480		$	—



(a)	See Note 2, Significant Accounting Policies.

(b)	See Note 10, Derivatives and Hedging Activity.

(c)	See Note 6, Secured and Unsecured Debt.

(d)	See Note 8, Noncontrolling Interests.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Estimated fair values	The estimated fair values of the Operating Partnership’s financial instruments either recorded or disclosed on a recurring basis as of March 31, 2015 and December 31, 2014 are summarized as follows (dollars in thousands):


								Fair Value at March 31, 2015, Using
		Total Carrying Amount in Statement of Financial Position at March 31, 2015			Fair Value Estimate at March 31, 2015			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Derivatives - Interest rate contracts (a)	$	17		$	17		$	—		$	17		$	—

	Total assets	$	17		$	17		$	—		$	17		$	—


	Derivatives - Interest rate contracts (a)	$	686		$	686		$	—		$	686		$	—

	Secured debt instruments - fixed rate: (b)
	Mortgage notes payable	376,207			388,821			—			—			388,821

	Fannie Mae credit facilities	333,735			352,765			—			—			352,765

	Secured debt instruments - variable rate: (b)
	Tax-exempt secured notes payable	27,000			27,000			—			—			27,000

	Fannie Mae credit facilities	192,760			192,760			—			—			192,760

	Total liabilities	$	930,388		$	962,032		$	—		$	686		$	961,346



								Fair Value at December 31, 2014, Using
		Total Carrying Amount in Statement of Financial Position at December 31, 2014			Fair Value Estimate at December 31, 2014			Quoted Prices in			Significant			Significant
								Active Markets			Other			Unobservable
								for Identical			Observable			Inputs
								Assets or			Inputs			(Level 3)
								Liabilities			(Level 2)
								(Level 1)
	Description:
	Derivatives - Interest rate contracts (a)	$	39		$	39		$	—		$	39		$	—

	Total assets	$	39		$	39		$	—		$	39		$	—


	Derivatives - Interest rate contracts (a)	$	918		$	918		$	—		$	918		$	—

	Secured debt instruments - fixed rate: (b)
	Mortgage notes payable	378,371			391,835			—			—			391,835

	Fannie Mae credit facilities	333,828			355,470			—			—			355,470

	Secured debt instruments - variable rate: (b)
	Tax-exempt secured notes payable	27,000			27,000			—			—			27,000

	Fannie Mae credit facilities	192,760			192,760			—			—			192,760

	Total liabilities	$	932,877		$	967,983		$	—		$	918		$	967,065



	(a)	See Note 7, Derivatives and Hedging Activity.

	(b)	See Note 4, Debt.

Derivatives_and_Hedging_Activi2

Derivatives and Hedging Activity (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Outstanding interest rate derivatives	As of March 31, 2015, the Company had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		9		$	565,000

	Interest rate caps		3		$	243,079

	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, the Company had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		$	96,409


Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet	The tables below present the fair value of the Company’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Asset Derivatives								Liability Derivatives
		(included in *Other assets*)								(included in *Other liabilities*)
		Fair Value at:								Fair Value at:
		March 31,				December 31,				March 31,				December 31,
		2015				2014				2015				2014
	Derivatives designated as hedging instruments:
	Interest rate products	$	28			86				$	17,112			$	10,368

	Derivatives not designated as hedging instruments:
	Interest rate products	$	1			$	2			$	—			$	—

Effect of Company's derivative financial instruments on Consolidated Statements of Operation	The tables below present the effect of the Company’s derivative financial instruments on the Consolidated Statements of Operations for the three months ended March 31, 2015 and 2014 (dollars in thousands):


	Derivatives in Cash Flow Hedging Relationships		Unrealized holding gain/(loss) Recognized in OCI								Gain/(Loss) Reclassified from Accumulated OCI into *Interest expense*								Gain/(Loss) Recognized in *Interest expense* (Ineffective Portion and Amount Excluded from Effectiveness Testing)
			(Effective Portion)								(Effective Portion)
			2015				2014				2015				2014				2015			2014
	Three Months Ended March 31,
	Interest rate products		$	(7,552	)		$	(55	)		$	(737	)		$	(1,532	)		$	—		$	—

Effect of Company's derivatives not designated as hedging instruments on the Consolidated Statements of Operations

			Gain/(Loss) Recognized in *Interest and other income/(expense), net*
	Derivatives Not Designated as Hedging Instruments		2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(1	)		$	—

Offsetting Assets [Table Text Block]

	Offsetting of Derivative Assets
		Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)				Gross Amounts Not Offset in the Consolidated Balance Sheets
														Financial Instruments				Cash Collateral Received			Net Amount
	March 31, 2015	$	29			$	—			$	29			$	—			$	—		$	29


	December 31, 2014	$	88			$	—			$	88			$	(27	)		$	—		$	61

	(a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.
Offsetting Liabilities [Table Text Block]

	Offsetting of Derivative Liabilities
		Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)				Gross Amounts Not Offset in the Consolidated Balance Sheets
														Financial Instruments				Cash Collateral Posted			Net Amount
	March 31, 2015	$	17,112			$	—			$	17,112			$	—			$	—		$	17,112


	December 31, 2014	$	10,368			$	—			$	10,368			$	(27	)		$	—		$	10,341

	(b) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.

Derivatives_and_Hedging_Activi3

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Tables)	3 Months Ended
	Mar. 31, 2015
Entity Information [Line Items]
Outstanding interest rate derivatives	As of March 31, 2015, the Company had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		9		$	565,000
	Interest rate swaps		9		$	565,000
	Interest rate caps		3		$	243,079
	Interest rate caps		3		$	243,079
	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, the Company had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		$	96,409
	Interest rate caps		1		$	96,409

Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet	The tables below present the fair value of the Company’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Asset Derivatives								Liability Derivatives
		(included in *Other assets*)								(included in *Other liabilities*)
		Fair Value at:								Fair Value at:
		March 31,				December 31,				March 31,				December 31,
		2015				2014				2015				2014
	Derivatives designated as hedging instruments:
	Interest rate products	$	28			86				$	17,112			$	10,368
	Interest rate products	$	28			86				$	17,112			$	10,368
	Derivatives not designated as hedging instruments:
	Interest rate products	$	1			$	2			$	—			$	—
	Interest rate products	$	1			$	2			$	—			$	—
Effect of Company's derivative financial instruments on Consolidated Statements of Operation	The tables below present the effect of the Company’s derivative financial instruments on the Consolidated Statements of Operations for the three months ended March 31, 2015 and 2014 (dollars in thousands):


	Derivatives in Cash Flow Hedging Relationships		Unrealized holding gain/(loss) Recognized in OCI								Gain/(Loss) Reclassified from Accumulated OCI into *Interest expense*								Gain/(Loss) Recognized in *Interest expense* (Ineffective Portion and Amount Excluded from Effectiveness Testing)
			(Effective Portion)								(Effective Portion)
			2015				2014				2015				2014				2015			2014
	Three Months Ended March 31,
	Interest rate products		$	(7,552	)		$	(55	)		$	(737	)		$	(1,532	)		$	—		$	—
	Interest rate products		$	(7,552	)		$	(55	)		$	(737	)		$	(1,532	)		$	—		$	—
Effect of Company's derivatives not designated as hedging instruments on the Consolidated Statements of Operations

			Gain/(Loss) Recognized in *Interest and other income/(expense), net*
	Derivatives Not Designated as Hedging Instruments		2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(1	)		$	—
	Interest rate products		$	(1	)		$	—
Offsetting Assets [Table Text Block]

	Offsetting of Derivative Assets
		Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)				Gross Amounts Not Offset in the Consolidated Balance Sheets
		Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Received			Net Amount
	March 31, 2015	$	29			$	—			$	29			$	—			$	—		$	29
	March 31, 2015	$	29			$	—			$	29			$	—			$	—		$	29

	December 31, 2014	$	88			$	—			$	88			$	(27	)		$	—		$	61
	December 31, 2014	$	88			$	—			$	88			$	(27	)		$	—		$	61
	(a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.
Offsetting Liabilities [Table Text Block]

	Offsetting of Derivative Liabilities
		Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)				Gross Amounts Not Offset in the Consolidated Balance Sheets
		Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Posted			Net Amount
	March 31, 2015	$	17,112			$	—			$	17,112			$	—			$	—		$	17,112
	March 31, 2015	$	17,112			$	—			$	17,112			$	—			$	—		$	17,112

	December 31, 2014	$	10,368			$	—			$	10,368			$	(27	)		$	—		$	10,341
	December 31, 2014	$	10,368			$	—			$	10,368			$	(27	)		$	—		$	10,341
	(b) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Outstanding interest rate derivatives	As of March 31, 2015, the Operating Partnership had the following outstanding interest rate derivatives designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		1		$	46,272
	Interest rate swaps		1		$	46,272
	Interest rate caps		2		$	166,341
	Interest rate caps		2		$	166,341
	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, we had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		89,220
	Interest rate caps		1		89,220
	As of March 31, 2015, the Operating Partnership had the following outstanding interest rate derivatives designated as cash flow hedges of interest rate risk (dollars in thousands):


	Interest Rate Derivative		Number of Instruments		Notional
	Interest rate swaps		1		$	46,272
	Interest rate swaps		1		$	46,272
	Interest rate caps		2		$	166,341
	Interest rate caps		2		$	166,341
	Derivatives not designated as hedges are not speculative and are used to manage the Company’s exposure to interest rate movements and other identified risks but do not meet the strict hedge accounting requirements of GAAP. Changes in the fair value of derivatives not designated in hedging relationships are recorded directly in earnings and resulted in no adjustment to earnings for the three months ended March 31, 2015 and 2014.
	As of March 31, 2015, we had the following outstanding derivatives that were not designated as hedges in qualifying hedging relationships (dollars in thousands):


	Product		Number of Instruments		Notional
	Interest rate caps		1		89,220
	Interest rate caps		1		89,220
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet	The table below presents the fair value of the Operating Partnership’s derivative financial instruments as well as their classification on the Consolidated Balance Sheets as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		Asset Derivatives								Liability Derivatives
		(included in *Other assets*)								(included in *Other liabilities*)
		Fair Value at:								Fair Value at:
		March 31,				December 31,				March 31,				December 31,
		2015				2014				2015				2014
	Derivatives designated as hedging instruments:
	Interest rate products	$	16			$	37			$	686			$	918
	Interest rate products	$	16			$	37			$	686			$	918

	Derivatives not designated as hedging instruments:
	Interest rate products	$	1			$	2			$	—			$	—
	Interest rate products	$	1			$	2			$	—			$	—
Effect of Company's derivative financial instruments on Consolidated Statements of Operation	The tables below present the effect of the derivative financial instruments on the Consolidated Statements of Operations for the three months ended March 31, 2015 and 2014 (dollars in thousands):


			Unrealized holding gain/(loss) Recognized in OCI								Gain/(Loss) Reclassified from Accumulated OCI into *Interest expense*
			(Effective Portion)								(Effective Portion)
	Derivatives in Cash Flow Hedging Relationships		2015				2014				2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(51	)		$	(51	)		$	(286	)		$	(623	)
Effect of Company's derivatives not designated as hedging instruments on the Consolidated Statements of Operations

			Gain/(Loss) Recognized in
			Interest and other income/(expense), net
	Derivatives Not Designated as Hedging Instruments		2015				2014
	Three Months Ended March 31,
	Interest rate products		$	(1	)		$	—
	Interest rate products		$	(1	)		$	—
Offsetting Assets [Table Text Block]	The General Partner has elected not to offset derivative positions in the consolidated financial statements. The table below presents the effect on the Operating Partnership’s financial position had the General Partner made the election to offset its derivative positions as of March 31, 2015 and December 31, 2014:


	Offsetting of Derivative Assets
		Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)				Gross Amounts Not Offset in the Consolidated Balance Sheets
		Gross Amounts of Recognized Assets				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Received			Net Amount
	March 31, 2015	$	17			$	—			$	17			$	—			$	—		$	17
	March 31, 2015	$	17			$	—			$	17			$	—			$	—		$	17

	December 31, 2014	$	39			$	—			$	39			$	—			$	—		$	39
	December 31, 2014	$	39			$	—			$	39			$	—			$	—		$	39
	(a) Amounts reconcile to the aggregate fair value of derivative assets in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.
Offsetting Liabilities [Table Text Block]

	Offsetting of Derivative Liabilities
		Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets				Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)				Gross Amounts Not Offset in the Consolidated Balance Sheets
		Gross Amounts of Recognized Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets								Financial Instruments				Cash Collateral Posted			Net Amount
	March 31, 2015	$	686			$	—			$	686			$	—			$	—		$	686
	March 31, 2015	$	686			$	—			$	686			$	—			$	—		$	686

	December 31, 2014	$	918			$	—			$	918			$	—			$	—		$	918
	December 31, 2014	$	918			$	—			$	918			$	—			$	—		$	918
	(b) Amounts reconcile to the aggregate fair value of derivative liabilities in the “Tabular Disclosure of Fair Values of Derivative Instruments on the Balance Sheet” located in this footnote.

Commitments_and_Contingencies_1

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Real estate commitments	The following summarizes the Company’s real estate commitments at March 31, 2015 (dollars in thousands):


		Number of	Costs Incurred			Expected Costs			Average Ownership
		Properties	to Date (a)			to Complete			Stake
	Wholly-owned — under development	1	$	196,653	(b)	$	21,047		100	%

	Wholly-owned — redevelopment	2	90,382		(b)	22,618			100	%

	Joint ventures:
	Unconsolidated joint ventures	4	285,730			189,037		(c)	Various

	Participating loan investments	1	75,647		(d)	16,362		(e)	0	%

			$	648,412		$	249,064


	(a)	Represents 100% of project costs incurred to date.

	(b)	Costs incurred to date include $11.1 million and $2.3 million of accrued fixed assets for development and redevelopment, respectively.

	(c)	Represents UDR’s proportionate share of expected remaining costs to complete.

	(d)	Represents the participating loan balance funded as of March 31, 2015.

	(e)	Represents UDR’s remaining participating loan commitment for Steele Creek.

Reportable_Segment_Tables

Reportable Segment (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations	The following table details rental income and NOI from continuing and discontinued operations for UDR’s reportable segments for the three months ended March 31, 2015 and 2014, and reconciles NOI to Net Income/(Loss) Attributable to UDR, Inc. in the Consolidated Statements of Operations (dollars in thousands):


		Three Months Ended
		March 31, (a)
		2015			2014
	Reportable apartment home segment rental income
	Same-Store Communities
	West Region	$	67,857		$	63,267

	Mid-Atlantic Region	42,795			42,049

	Southeast Region	27,829			26,497

	Northeast Region	20,892			19,803

	Southwest Region	14,107			13,467

	Non-Mature Communities/Other	33,567			29,317

	Total consolidated rental income	$	207,047		$	194,400


	Reportable apartment home segment NOI
	Same-Store Communities
	West Region	$	50,228		$	45,408

	Mid-Atlantic Region	29,288			28,835

	Southeast Region	18,547			17,872

	Northeast Region	15,566			14,546

	Southwest Region	8,536			8,358

	Non-Mature Communities/Other	21,410			17,105

	Total consolidated NOI	143,575			132,124

	Reconciling items:
	Joint venture management and other fees	12,706			3,687

	Property management	(5,694		)	(5,346		)
	Other operating expenses	(1,766		)	(1,935		)
	Real estate depreciation and amortization	(88,777		)	(88,533		)
	General and administrative	(12,152		)	(11,994		)
	Casualty-related recoveries/(charges), net	(996		)	(500		)
	Other depreciation and amortization	(1,623		)	(1,080		)
	Income/(loss) from unconsolidated entities	59,159			(3,565		)

	Interest expense	(28,800		)	(32,884		)
	Interest and other income/(expense), net	360			1,415

	Tax benefit/(expense), net	425			3,329

	Gain/(loss) on sale of real estate owned, net of tax	—			24,294

	Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership	(2,588		)	(647		)
	Net (income)/loss attributable to noncontrolling interests	(7		)	(4		)
	Net income/(loss) attributable to UDR, Inc.	$	73,822		$	18,361



	(a)	Same-Store Community population consisted of 36,063 apartment homes.

Details of assets of UDR's reportable segments	The following table details the assets of UDR’s reportable segments as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,			December 31,
		2015			2014
	Reportable apartment home segment assets:
	Same-Store Communities:
	West Region	$	2,626,770		$	2,620,242

	Mid-Atlantic Region	1,536,389			1,533,993

	Southeast Region	788,668			786,438

	Northeast Region	1,078,431			1,076,656

	Southwest Region	441,888			440,721

	Non-Mature Communities/Other	1,981,502			1,925,209

	Total assets	8,453,648			8,383,259

	Accumulated depreciation	(2,522,100		)	(2,434,772		)
	Total assets — net book value	5,931,548			5,948,487

	Reconciling items:
	Cash and cash equivalents	6,274			15,224

	Restricted cash	23,266			22,340

	Deferred financing costs, net	21,676			22,686

	Notes receivable, net	15,494			14,369

	Investment in and advances to unconsolidated joint ventures, net	763,540			718,226

	Other assets	96,713			105,202

	Total consolidated assets	$	6,858,511		$	6,846,534

Reportable_Segments_UNITED_DOM1

Reportable Segments (UNITED DOMINION REALTY, L.P.) (Tables) (United Dominion Reality L.P. [Member])	3 Months Ended
	Mar. 31, 2015
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Reportable segments information	The following table details rental income and NOI from continuing and discontinued operations for the Operating Partnership’s reportable segments for the three months ended March 31, 2015 and 2014, and reconciles NOI to Net income/(loss) attributable to OP unitholders in the Consolidated Statements of Operations (dollars in thousands):


		Three Months Ended
		March 31, (a)
		2015				2014
	Reportable apartment home segment rental income
	Same-Store Communities
	West Region	$	47,815			$	44,238

	Mid-Atlantic Region	17,249				17,246

	Southeast Region	11,679				11,131

	Northeast Region	15,072				14,268

	Southwest Region	6,737				6,553

	Non-Mature Communities/Other	11,543				8,934

	Total consolidated rental income	$	110,095			$	102,370

	Reportable apartment home segment NOI
	Same-Store Communities
	West Region	$	35,277			$	32,089

	Mid-Atlantic Region	11,466				11,565

	Southeast Region	7,710				7,457

	Northeast Region	11,572				10,638

	Southwest Region	4,213				4,217

	Non-Mature Communities/Other	7,877				6,451

	Total consolidated NOI	78,115				72,417

	Reconciling items:
	Property management	(3,027		)		(2,815		)
	Other operating expenses	(1,490		)		(1,436		)
	Real estate depreciation and amortization	(44,478		)		(44,271		)
	General and administrative	(5,639		)		(6,970		)
	Casualty-related recoveries/(charges), net	(593		)		(500		)
	Interest expense	(10,771		)		(10,014		)
	Gain/(loss) on sale of real estate owned	24,623				24,402

	Net (income)/loss attributable to noncontrolling interests	(394		)		(280		)
	Net income/(loss) attributable to OP unitholders	$	36,346			$	30,533



	(a)	Same-store consists of 19,209 apartment homes.
	The following table details the assets of the Operating Partnership’s reportable segments as of March 31, 2015 and December 31, 2014 (dollars in thousands):


		March 31,				December 31, 2014
		2015
	Reportable apartment home segment assets
	Same-Store Communities
	West Region	$	1,690,647			$	1,686,127

	Mid-Atlantic Region	714,425				713,093

Southeast Region	334,282				333,428

Northeast Region	778,378				777,376

Southwest Region	229,627				228,996

Non-Mature Communities/Other	501,436				499,750

Total assets	4,248,795				4,238,770

Accumulated depreciation	(1,447,513		)		(1,403,303		)
Total assets - net book value	2,801,282				2,835,467

Reconciling items:
Cash and cash equivalents	826				502

Restricted cash	14,441				13,811

Deferred financing costs, net	4,118				4,475

Other assets	22,714				24,029

Total consolidated assets	$	2,843,381			$	2,878,284

Consolidation_and_Basis_of_Pre2

Consolidation and Basis of Presentation (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred Tax Assets, Net	7.6
Consolidation And Basis Of Presentation (Textual) [Abstract]
Operating Partnership outstanding units	183,278,698
Non-affiliated Partners [Member]
Consolidation And Basis Of Presentation (Textual) [Abstract]
OP units outstanding related to limited partner	9,164,939	9,165,473
Percentage of units outstanding in Heritage OP	5.00%	5.00%
Limited Partner [Member]
Consolidation And Basis Of Presentation (Textual) [Abstract]
Percentage of units outstanding in Heritage OP	95.00%
General Partner [Member]
Consolidation And Basis Of Presentation (Textual) [Abstract]
OP units outstanding related to limited partner	174,113,759
Non-affiliated Partners [Member]
Consolidation And Basis Of Presentation (Textual) [Abstract]
OP units outstanding related to limited partner	9,164,939
Percentage of units outstanding in Heritage OP	5.00%

Consolidation_and_Basis_of_Pre3

Consolidation and Basis of Presentation (UNITED DOMINION REALTY, L.P.) (Details)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
	Apartment_Homes
	Communities
	Markets
Entity Information [Line Items]
Number of Real Estate Properties	138
Number of apartments owned (in apartments homes)	39,956
Operating Partnership outstanding units	183,278,698
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Rental revenues percent of General Partner's consolidated rental revenues	53.00%	53.00%
Number of Real Estate Properties	68
Number of markets operating within (in markets)	17
Number of apartments owned (in apartments homes)	20,809
OP units outstanding related to general partner	110,883		110,883
OP units outstanding related to limited partner	183,167,815		183,167,815
Non-affiliated Partners [Member]
Entity Information [Line Items]
OP units outstanding related to limited partner	9,164,939		9,165,473
Percentage of units outstanding in Heritage OP	5.00%		5.00%
Limited Partner [Member]
Entity Information [Line Items]
Percentage of units outstanding in Heritage OP	95.00%
General Partner [Member]
Entity Information [Line Items]
OP units outstanding related to limited partner	174,113,759
Non-affiliated Partners [Member]
Entity Information [Line Items]
OP units outstanding related to limited partner	9,164,939
Percentage of units outstanding in Heritage OP	5.00%

Significant_Accounting_Policie5

Significant Accounting Policies (Details) (USD $)	3 Months Ended
Significant Accounting Policies (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Accounting Policies [Line Items]
Current Income Tax Expense (Benefit)	$0
Deferred Tax Assets, Net	7,600,000
Significant Accounting Policies (Textual) [Abstract]
Notes receivable	15,494,000		14,369,000
Note maturity public capital threshold	5,000,000
Note receivable interest income	400,000	1,200,000
Net of a valuation allowance	100,000
Tax benefit/(expense), net	-425,000	-3,329,000
Recognition and evaluation of tax position, whether a tax position is more likely	not (greater than 50 percent probability)
Unrecognized tax benefit, accrued interest or penalties due to examination	0
Proceeds from Sale and Collection of Notes Receivable	-1,125,000	-1,535,000
Interest Income, Related Party	0	0
Note due February 2017 [Member]
Accounting Policies [Line Items]
Increase (Decrease) in Notes Receivables	1,100,000
Note Receivable Interest Rate	10.00%
Significant Accounting Policies (Textual) [Abstract]
Notes receivable			11,869,000
Note maturity public capital threshold	5,000,000
Aggregate Commitment on Note Receivable	12,994,000
Other [Member]
Accounting Policies [Line Items]
Note Receivable Interest Rate	8.00%
Significant Accounting Policies (Textual) [Abstract]
Notes receivable	2,500,000		2,500,000
Aggregate Commitment on Note Receivable	2,500,000
RedeemableNoncontrollingInterest [Member]
Accounting Policies [Line Items]
Comprehensive (loss)/income attributable to non-controlling interests	($225,000)	$56,000

Real_Estate_Owned_Details

Real Estate Owned (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Summary of carrying amounts for real estate owned (at cost)
Land	$1,984,019
Depreciable property - held and used:
Building, Improvements, and Furniture, Fixtures and Equipment	6,272,976	6,225,406
Under development:
Real estate under development (net of accumulated depreciation of $142 and $0, respectively)	196,511	177,632
Real estate owned	8,453,648	8,383,259
Real Estates Owned Accumulated Depreciation	2,522,100	2,434,772
Real estate owned, net	5,931,548	5,948,487
Land [Member]
Under development:
Real estate under development (net of accumulated depreciation of $142 and $0, respectively)	24,584	1,980,221
Building and Building Improvements [Member]
Depreciable property - held and used:
Real Estate Held-for-sale		24,584
Construction in progress [Member]
Under development:
Real estate under development (net of accumulated depreciation of $142 and $0, respectively)	172,069
Furniture and Fixtures [Member]
Depreciable property - held and used:
Real Estate Held-for-sale		$153,048

Real_Estate_Owned_Details_Text

Real Estate Owned (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
	Apartment_Homes
	Communities
	States
Real Estate Properties [Line Items]
Communities Held For Sale	1
Real Estate Owned (Textual) [Abstract]
Number of states in which there are owned and consolidated communities	10
Number of apartment homes owned and consolidated by the Company	39,956
Number of Real Estate Properties	138
Development costs excluding direct costs and capitlized interest	$2,200,000	$3,400,000
Interest capitalized during period	4,800,000	5,300,000
Other Cost and Expense, Operating	1,766,000	1,926,000
Payments for (Proceeds from) Investments	0	47,922,000
Gains/(loss) on sales of real estate, net of tax	0	24,294,000
Casualty-related (recoveries)/charges, net	-996,000	-500,000
Casualty (Recoveries)/Charges	-996,000	-500,000
Unconsolidated Joint Venture Four Texas [Member]
Real Estate Owned (Textual) [Abstract]
Proceeds from Sale of Property, Plant, and Equipment	43,500,000
Gain (Loss) on Disposition of Property Plant Equipment	59,100,000
1745 Shea [Member]
Real Estate Owned (Textual) [Abstract]
Square Footage	120,000
UDR, Inc. [Member]
Real Estate Owned (Textual) [Abstract]
Square Footage	44,000
United Dominion Reality L.P. [Member]
Real Estate Owned (Textual) [Abstract]
Number of states in which there are owned and consolidated communities	9
Number of apartment homes owned and consolidated by the Company	20,809
Number of Real Estate Properties	68
Development costs excluding direct costs and capitlized interest	133,000	1,000,000
Interest capitalized during period	0	800,000
Other Cost and Expense, Operating	1,490,000	1,436,000
Gains/(loss) on sales of real estate, net of tax	24,623,000	24,402,000
Casualty (Recoveries)/Charges	-593,000	-500,000	500,000
Operating Community [Member]
Real Estate Owned (Textual) [Abstract]
Gain (Loss) on Disposition of Property Plant Equipment	23,300,000
Operating Community [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Real Estate Owned (Textual) [Abstract]
Number of Real Estate Properties	3
Operating Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Real Estate Owned (Textual) [Abstract]
Number of Real Estate Properties	8
Development Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Real Estate Owned (Textual) [Abstract]
Number of Real Estate Properties	0
Land [Member]
Real Estate Owned (Textual) [Abstract]
Gain (Loss) on Disposition of Property Plant Equipment	1,100,000
Office Building [Member] \| 1745 Shea [Member]
Real Estate Owned (Textual) [Abstract]
Property, Plant and Equipment, Additions	$24,000,000

Real_Estate_Owned_UNITED_DOMIN2

Real Estate Owned (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Summary of carrying amounts for real estate owned (at cost)
Land	$1,984,019
Under development:
Real estate under development (net of accumulated depreciation of $513 and $0, respectively)	196,511	177,632
Real estate owned	8,453,648	8,383,259
Less: accumulated depreciation	-2,521,958	-2,434,772
Real estate owned, net	5,931,548	5,948,487
Land [Member]
Under development:
Real estate under development (net of accumulated depreciation of $513 and $0, respectively)	24,584	1,980,221
Construction in progress [Member]
Under development:
Real estate under development (net of accumulated depreciation of $513 and $0, respectively)	172,069
United Dominion Reality L.P. [Member]
Summary of carrying amounts for real estate owned (at cost)
Land	1,008,358	1,008,014
Depreciable property - held and used:
Building, improvements, and furniture, fixture and equipment	3,240,437	3,230,756
Under development:
Real estate owned	4,248,795	4,238,770
Less: accumulated depreciation	-1,447,513	-1,403,303
Real estate owned, net	$2,801,282	$2,835,467

Real_Estate_Owned_UNITED_DOMIN3

Real Estate Owned (UNITED DOMINION REALTY, L.P.) (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
	Apartment_Homes
	Communities
	States
Real Estate Owned (Textual) [Abstract]
Number of communities owned (in communities)	138
Number of states operating within (in states)	10
Number of apartments owned (in apartments homes)	39,956
Number of communities acquired apartment homes are within	0
Development costs excluding direct costs and capitlized interest	$2,200,000	$3,400,000
Interest capitalized during period	4,800,000	5,300,000
Other Cost and Expense, Operating	1,766,000	1,926,000
Gains/(loss) on sales of real estate, net of tax	0	24,294,000
Casualty-related (recoveries)/charges, net	-996,000	-500,000
Casualty (Recoveries)/Charges	-996,000	-500,000
Payments for (Proceeds from) Investments	0	47,922,000
United Dominion Reality L.P. [Member]
Real Estate Owned (Textual) [Abstract]
Number of communities owned (in communities)	68
Number of states operating within (in states)	9
Number of apartments owned (in apartments homes)	20,809
Development costs excluding direct costs and capitlized interest	133,000	1,000,000
Interest capitalized during period	0	800,000
Other Cost and Expense, Operating	1,490,000	1,436,000
Gains/(loss) on sales of real estate, net of tax	24,623,000	24,402,000
Casualty (Recoveries)/Charges	($593,000)	($500,000)	$500,000

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended
Discontinued Operations (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014
Disposal Group, Including Discontinued Operation, Interest Expense	$0	$1,000
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	0	9,000
Discontinued Operations (Textual) [Abstract]
Communities held for sale (in communities)	1
Summary of income from discontinued operations
Rental expenses	0	48,000
Real estate depreciation	0	125,000
Income/(loss) from discontinued operations, net of tax	0	-87,000
Income/(loss) from discontinued operations attributable to common stockholders	0	-84,000
Operating Community [Member]
Gain (Loss) on Disposition of Property Plant Equipment	23,300,000
Land [Member]
Gain (Loss) on Disposition of Property Plant Equipment	$1,100,000

Joint_Ventures_Details

Joint Ventures (Details) (USD $)	3 Months Ended
Joint Ventures (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014
Financial information relating to unconsolidated joint ventures operations
UDR income/(loss) from unconsolidated entities	$59,159,000	($3,565,000)
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	763,540,000			718,226,000
Deferred gains on the sale of depreciable property	5,600,000			28,500,000
Number of Real Estate Properties	138
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Income/(loss) from discontinued operations	182,488,000	-29,997,000
Financial information relating to unconsolidated joint ventures operations
Total revenues	54,546,000		38,955,000
Equity Method Investment Summarized Financial Information Property Operating Expense	-20,168,000	-14,360,000
Real estate depreciation and amortization	-19,351,000		-14,688,000
Net income /(loss)	181,454,000		-32,241,000
Combined summary of balance sheets relating to unconsolidated joint ventures
Total real estate, net	2,970,102,000			2,941,803,000
Equity Method of Investment Summarized Financial Information, Assets Sold or Held For Sale	0			216,196,000
Equity Method Investment Summarized Financial Information Cash and cash equivalents	29,544,000			32,544,000
Equity Method Investment Summarized Financial Information Other assets	31,162,000			28,707,000
Total assets	3,030,808,000			3,219,250,000
Amount due to UDR	4,691,000			2,997,000
Third party debt	1,514,886,000			1,504,477,000
Equity Method of Investment Summarized Financial Information, Liabilities Sold or Held For Sale	0			229,706,000
Equity Method Investment Summarized Financial Information Accounts payable and accrued liabilities	52,146,000			44,335,000
Total liabilities	1,571,723,000			1,781,515,000
Total equity	1,459,085,000			1,437,735,000
Equity Method Investment, Summarized Financial Information, Liabilities and Equity	3,030,808,000			3,219,250,000
Investment in and advances to unconsolidated joint ventures, net	687,893,000			655,519,000
Equity Method of Investment Summarized Financial Information Operating income/(loss)	15,027,000	9,907,000
Equity Method Investment Summarized Financial Information Interest expense	-16,061,000	-12,151,000
Unconsolidated Joint Venture Four Texas [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Deferred gains on the sale of depreciable property	24,200,000
Operating Community [Member] \| Unconsolidated Joint Venture UDR Met Life I Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	13,473,000			13,306,000
Equity Method Investment, Ownership Percentage	15.70%			15.70%
Number of apartment homes	0
Number of Real Estate Properties	4
Operating Community [Member] \| Unconsolidated Joint Venture UDR MetLife II Partnership [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	429,635,000			431,277,000
Equity Method Investment, Ownership Percentage	50.00%			50.00%
Number of apartment homes	4,642
Number of Real Estate Properties	21
Operating Community [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	78,669,000			80,302,000
Equity Method Investment, Ownership Percentage	50.00%			50.00%
Number of apartment homes	1,130
Number of Real Estate Properties	3
Operating Community [Member] \| Unconsolidated Joint Venture Three [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	20,435,000			21,596,000
Equity Method Investment, Ownership Percentage	30.00%			30.00%
Number of apartment homes	660
Number of Real Estate Properties	3
Operating Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Equity Method Investment, Ownership Percentage	0.00%			20.00%
Number of Real Estate Properties	8
Operating Community [Member] \| Unconsolidated Joint Venture Other MetLife [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	145,681,000			134,939,000
Equity Method Investment, Ownership Percentage	50.60%			50.60%
Number of apartment homes	1,437
Number of Real Estate Properties	1
Land Parcel [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Number of Real Estate Properties	6
Development Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	0			-25,901,000
Number of apartment homes	0
Number of Real Estate Properties	0
Development Community [Member] \| Unconsolidated Joint Venture Other MetLife [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Number of Real Estate Properties	4
Development Community [Member] \| Participating Loan Investment Steele Creek Denver Colorado [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Investment in and advances to unconsolidated joint ventures, net	75,647,000			62,707,000
Income from Participating Loan	$1,154	$321,000
Participating Loan, Interest Rate, Stated Percentage	6.50%
Participating Loan Years to Maturity	2 years 3 months 18 days
Land [Member] \| Unconsolidated Joint Venture Other MetLife [Member]
Combined summary of balance sheets relating to unconsolidated joint ventures
Number of Real Estate Properties	1

Joint_Ventures_Details_Textual

Joint Ventures (Details Textual) (USD $)	3 Months Ended
Joint Ventures (Details Textual) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	138
Community Threshold, Period Above Occupancy Threshold	3 months
Secured Debt	$1,370,673,000		$1,361,529,000
Joint Ventures
Real Estate Owned Gross	8,453,648,000		8,383,259,000
Unamortized discount	7,000,000		6,700,000
First installment of payable incurred in partial consideration for acquisition of ownership interest in joint venture	194,893,000
Second installment of payable incurred in partial consideration for acquisition of ownership interest in joint venture	242,691,000
Interest expense	-28,800,000	32,884,000
Company's equity investment in joint venture	763,540,000		718,226,000
Deferred profit from the sale of properties	5,600,000		28,500,000
Management fees for our involvement in the joint ventures	2,600,000	3,300,000
Fee Income from the Sale of Real Estate	9,634,000	0
Unconsolidated Joint Venture Four Texas [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Sale of Property, Plant, and Equipment	43,500,000
Joint Ventures
Deferred profit from the sale of properties	24,200,000
Fee Income from the Sale of Real Estate	9,600,000
Gain (Loss) on Disposition of Property Plant Equipment	59,100,000
Unconsolidated Joint Venture 399 Fremont [Member]
Schedule of Equity Method Investments [Line Items]
Number of apartments of development community			0
Unconsolidated Joint Venture Wolff [Member]
Schedule of Equity Method Investments [Line Items]
Total Fixed Price Option Sales Price	597,000,000
Number of Markets Operating Within	3
Preferred Return Interest Rate	650.00%
Community Threshold, Percent Occupancy Threshold	8000.00%
Community Threshold, Period Above Occupancy Threshold	90 days
Fixed Price Option Period	1 year
Joint Ventures
Equity Method Investment Cost of Ownership Interest	136,000,000
Equity Method Investment, Ownership Percentage	4800.00%
Land [Member]
Joint Ventures
Gain (Loss) on Disposition of Property Plant Equipment	1,100,000
Land [Member] \| Unconsolidated Joint Venture Other MetLife [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	1
Operating Community [Member]
Joint Ventures
Gain (Loss) on Disposition of Property Plant Equipment	23,300,000
Operating Community [Member] \| Unconsolidated Joint Venture Vitruvian Park [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	3
Number of apartment homes	1,130
Joint Ventures
Company's equity investment in joint venture	78,669,000		80,302,000
Equity Method Investment, Ownership Percentage	50.00%		50.00%
Operating Community [Member] \| Unconsolidated Joint Venture UDR Met Life I Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	4
Number of apartment homes	0
Joint Ventures
Company's equity investment in joint venture	13,473,000		13,306,000
Equity Method Investment, Ownership Percentage	15.70%		15.70%
Operating Community [Member] \| Unconsolidated Joint Venture UDR MetLife II Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	21
Number of apartment homes	4,642
Joint Ventures
Company's equity investment in joint venture	429,635,000		431,277,000
Equity Method Investment, Ownership Percentage	50.00%		50.00%
Operating Community [Member] \| Unconsolidated Joint Venture Three Washington DC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	3
Number of apartment homes	660
Joint Ventures
Company's equity investment in joint venture	20,435,000		21,596,000
Equity Method Investment, Ownership Percentage	30.00%		30.00%
Operating Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	8
Joint Ventures
Equity Method Investment, Ownership Percentage	0.00%		20.00%
Operating Community [Member] \| Unconsolidated Joint Venture Other MetLife [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	1
Number of apartment homes	1,437
Joint Ventures
Company's equity investment in joint venture	145,681,000		134,939,000
Equity Method Investment, Ownership Percentage	50.60%		50.60%
Operating Community [Member] \| Unconsolidated Joint Venture Wolff [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	2
Number of apartment homes	1,533
Development Community [Member] \| Unconsolidated Joint Venture Four Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	0
Number of apartment homes	0
Joint Ventures
Company's equity investment in joint venture	$0		($25,901,000)
Development Community [Member] \| Unconsolidated Joint Venture Other MetLife [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	4
Development Community [Member] \| Unconsolidated Joint Venture Wolff [Member]
Schedule of Equity Method Investments [Line Items]
Number of Real Estate Properties	5

Secured_and_Unsecured_Debt_Det

Secured and Unsecured Debt (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Secured debt instruments
Weighted average interest rate	3.62%
Long-term Debt	$3,516,669	$3,583,105
Unsecured Debt	2,145,996	2,221,576
Weighted Average Years to Maturity	4 years 4 months 9 days
Line of Credit Facility, Amount Outstanding	1,500	1,900
Fixed Rate Debt [Member]
Secured debt instruments
Principal outstanding	978,440	969,296
Weighted average interest rate	5.28%
Weighted Average Years to Maturity	2 years 9 months 10 days
Number of Communities Encumbered	29
Variable Rate Debt [Member]
Secured debt instruments
Principal outstanding	392,233	392,233
Weighted average interest rate	1.44%
Weighted Average Years to Maturity	5 years 4 months 24 days
Number of Communities Encumbered	10
Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Weighted average interest rate	5.49%
Weighted Average Years to Maturity	1 year 4 months 20 days
Number of Communities Encumbered	7
Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Weighted average interest rate	1.94%
Weighted Average Years to Maturity	1 year 9 months 25 days
Number of Communities Encumbered	1
Tax-exempt secured notes payable [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Weighted average interest rate	0.76%
Weighted Average Years to Maturity	7 years 11 months 8 days
Number of Communities Encumbered	2
Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Debt, Weighted Average Interest Rate	5.12%
Weighted Average Years to Maturity	3 years 9 months 10 days
Number of Communities Encumbered	22
Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Debt Instrument, Interest Rate at Period End	1.62%
Weighted Average Years to Maturity	4 years 11 months 8 days
Number of Communities Encumbered	7
Secured Debt [Member]
Secured debt instruments
Principal outstanding	1,370,673	1,361,529
Weighted average interest rate	4.18%
Long-term Debt	1,370,673
Weighted Average Years to Maturity	3 years 6 months 10 days
Number of Communities Encumbered	39
Secured Debt [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Long-term Debt	978,440
Secured Debt [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Long-term Debt	392,233
Unsecured Revolving Credit Facility due October 2015 [Member]
Secured debt instruments
Weighted average interest rate	1.08%
Weighted Average Years to Maturity	2 years 8 months 4 days
Line of Credit Facility, Amount Outstanding	389,000	152,500
ThreePointSevenTermNotesDueOctober2020 [Member]
Secured debt instruments
Weighted average interest rate	3.70%
Senior Notes	299,956	299,954
Weighted Average Years to Maturity	5 years 6 months
Four Point Six Three Percent Term Medium Notes Due January Two Thousand Twenty-Two [Member]
Secured debt instruments
Weighted average interest rate	4.63%
Senior Notes	397,567	397,477
Weighted Average Years to Maturity	6 years 9 months 10 days
3.75 MTN Due July 2024 [Member]
Secured debt instruments
Weighted average interest rate	3.75%
Senior Notes	299,036	299,010
Weighted Average Years to Maturity	9 years 3 months
1.67% Term Notes due December 2016 [Member]
Secured debt instruments
Weighted average interest rate	1.32%
Senior Notes	35,000	35,000
Weighted Average Years to Maturity	3 years 2 months 4 days
2.68% Term Notes due December 2016 [Member]
Secured debt instruments
Weighted average interest rate	1.53%
Senior Notes	100,000	100,000
Weighted Average Years to Maturity	3 years 2 months 4 days
Five Point Two Five Percent, Medium Term Notes, Due January 2015 [Member]
Secured debt instruments
Weighted average interest rate	0.00%
Senior Notes	0	325,169
Weighted Average Years to Maturity	0 years
Five Point Two Five Percent, Medium Term Notes, Due January 2016 [Member]
Secured debt instruments
Weighted average interest rate	5.25%
Senior Notes	83,260	83,260
Weighted Average Years to Maturity	9 months 14 days
6.21 Medium Term Note, Due January 2016 [Member]
Secured debt instruments
Weighted average interest rate	6.21%
Senior Notes	12,865	0
Weighted Average Years to Maturity	1 year 3 months 3 days
2.90% Term Notes due January 2016 [Member]
Secured debt instruments
Weighted average interest rate	1.70%
Senior Notes	215,000	215,000
Weighted Average Years to Maturity	3 years 2 months 4 days
Eight Point Five Zero Percent, Debentures, Due September 2024 [Member]
Secured debt instruments
Weighted average interest rate	8.50%
Senior Notes	15,644	15,644
Weighted Average Years to Maturity	9 years 5 months 15 days
Four Point Two Five Percentage Medium-Term Notes due June 2018 [Member]
Secured debt instruments
Weighted average interest rate	4.25%
Senior Notes	298,642	298,535
Weighted Average Years to Maturity	3 years 2 months 1 day
Other [Member]
Secured debt instruments
Senior Notes	26	27
Unsecured Debt [Member]
Secured debt instruments
Weighted average interest rate	3.26%
Long-term Debt	2,145,996
Unsecured Debt	2,145,996	2,221,576
Weighted Average Years to Maturity	4 years 10 months 17 days
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Principal outstanding	411,271	401,210
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Principal outstanding	31,337	31,337
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Line of Credit [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Secured debt instruments
Principal outstanding	567,169	568,086
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Line of Credit [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Secured debt instruments
Principal outstanding	$266,196	$266,196

Secured_and_Unsecured_Debt_Det1

Secured and Unsecured Debt (Details 1) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2013	Dec. 31, 2014
Line of Credit Facility [Line Items]
Unamortized discount	$7,000		$6,700
Secured credit facilities
Borrowings outstanding	1,500		1,900
Five Point Two Five Percent, Medium Term Notes, Due January 2015 [Member]
Line of Credit Facility [Line Items]
Unamortized discount	0		6
Fannie Mae [Member]
Secured credit facilities
Borrowings outstanding	833,365		834,282
Weighted average daily borrowings during the period ended	833,697	835,873
Maximum daily borrowings during the period ended	834,003	837,564
Weighted average interest rate during the period ended	4.00%	4.10%
Interest rate at the end of the period	4.00%		4.00%
Four Point Two Five Percentage Medium-Term Notes due June 2018 [Member]
Line of Credit Facility [Line Items]
Unamortized discount	1,358		1,465
Three point seven percent medium term note due October 2020 [Member]
Line of Credit Facility [Line Items]
Unamortized discount	44		46
Four Point Six Three Percent Term Medium Notes Due January Two Thousand Twenty-Two [Member]
Line of Credit Facility [Line Items]
Unamortized discount	2,433		2,523
3.75 MTN Due July 2024 [Member]
Line of Credit Facility [Line Items]
Unamortized discount	$964		$990

Secured_and_Unsecured_Debt_Det2

Secured and Unsecured Debt (Details 2) (USD $)	3 Months Ended
Secured and Unsecured Debt (Details 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Secured Debt, Encumbers Real Estate Owned, Amount	$2,300,000,000
Secured Debt, Encumbers Real Estate Owned, Percent	26.70%
Debt Instrument Weighted Average Years to Maturity	4 years 4 months 9 days
Unamortized discount	7,000,000	6,700,000
Aggregate maturities of secured debt
2014	194,893,000
2015	242,691,000
2016	663,219,000
2017	874,916,000
2018	313,571,000
Thereafter	1,227,379,000
Total	1,370,673,000	1,361,529,000
Secured Debt, Unencumbered Real Estate Owned, Amount	6,200,000,000
Secured Debt, Unencumbered Real Estate Owned, Percent	73.30%
Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	2 years 9 months 10 days
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	5 years 4 months 24 days
ThreePointSevenTermNotesDueOctober2020 [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	5 years 6 months
2.68% Term Notes due December 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	3 years 2 months 4 days
Four Point Six Three Percent Term Medium Notes Due January Two Thousand Twenty-Two [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	6 years 9 months 10 days
Unamortized discount	2,433,000	2,523,000
Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	1 year 4 months 20 days
Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	1 year 9 months 25 days
Tax Exempt Notes Payable [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	7 years 11 months 8 days
Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	3 years 9 months 10 days
Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	4 years 11 months 8 days
3.75 MTN Due July 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	9 years 3 months
Unamortized discount	964,000	990,000
Five Point Two Five Percent, Medium Term Notes, Due January 2015 [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	0 years
Unamortized discount	$0	$6,000

Secured_and_Unsecured_Debt_Det3

Secured and Unsecured Debt (Details 3) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Summary of unsecured debt
Borrowings outstanding at end of period	$1,500	$1,900
Unsecured Debt, Total	2,145,996	2,221,576
Unamortized discount	7,000	6,700
Borrowings outstanding under an unsecured credit facility due October 2015 [Member]
Summary of unsecured debt
Borrowings outstanding at end of period	389,000	152,500
4.63% Medium-Term Notes due January 2022 [Member]
Summary of unsecured debt
Senior Unsecured Notes	397,567	397,477
Unamortized discount	2,433	2,523
1.67% Term Notes due December 2016 [Member]
Summary of unsecured debt
Senior Unsecured Notes	35,000	35,000
2.68% Term Notes due December 2016 [Member]
Summary of unsecured debt
Senior Unsecured Notes	100,000	100,000
5.25% Medium-Term Notes due January 2015 [Member]
Summary of unsecured debt
Senior Unsecured Notes	0	325,169
Unamortized discount	0	6
5.25% Medium-Term Notes due January 2016 [Member]
Summary of unsecured debt
Senior Unsecured Notes	83,260	83,260
2.90% Term Notes due January 2016 [Member]
Summary of unsecured debt
Senior Unsecured Notes	215,000	215,000
8.50% Debentures due September 2024 [Member]
Summary of unsecured debt
Senior Unsecured Notes	15,644	15,644
4.25% Medium-Term Notes due June 2018 [Member]
Summary of unsecured debt
Senior Unsecured Notes	298,642	298,535
Unamortized discount	1,358	1,465
Other [Member]
Summary of unsecured debt
Senior Unsecured Notes	$26	$27

Secured_and_Unsecured_Debt_Det4

Secured and Unsecured Debt (Details 4) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Borrowings outstanding at end of period	$1,500		$1,900
Unsecured Commercial Bank Credit Facility [Member]
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	900,000		900,000
Weighted average daily borrowings during the period ended	356,043	291,761
Maximum daily borrowings during the period ended	449,500	625,000
Weighted average interest rate during the period ended	1.20%	1.20%
Interest rate at the end of the period	1.10%		1.10%
Unsecured Revolving Credit Facility due October 2015 [Member]
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Borrowings outstanding at end of period	$389,000		$152,500

Secured_and_Unsecured_Debt_Det5

Secured and Unsecured Debt (Details 5) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Aggregate maturities of unsecured debt
2014	$194,893
2015	242,691
2016	663,219
2017	874,916
2018	313,571
Thereafter	1,227,379
Unsecured Debt, Total	2,145,996	2,221,576
Long-term Debt	3,516,669	3,583,105
Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	194,779
2015	148,223
2016	274,219
2017	226,472
2018	313,571
Thereafter	213,409
Long-term Debt	1,370,673
Unsecured Debt [Member]
Aggregate maturities of unsecured debt
2014	114
2015	94,468
2016	389,000
2017	648,444
2018	0
Thereafter	1,013,970
Unsecured Debt, Total	2,145,996	2,221,576
Long-term Debt	2,145,996
Fixed Rate Debt [Member] \| Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	194,779
2015	148,223
2016	177,882
2017	121,685
2018	245,871
Thereafter	90,000
Long-term Debt	978,440
Variable Rate Debt [Member] \| Secured Debt [Member]
Aggregate maturities of unsecured debt
2014	0
2015	0
2016	96,337
2017	104,787
2018	67,700
Thereafter	123,409
Long-term Debt	$392,233

Secured_and_Unsecured_Debt_Det6

Secured and Unsecured Debt (Details Textual) (USD $)	3 Months Ended	0 Months Ended	3 Months Ended
Secured and Unsecured Debt (Details Textual) (USD $)	Mar. 31, 2015	Jun. 27, 2014	Mar. 31, 2014	Dec. 31, 2014
Secured Debt (Textual) [Abstract]
Secured debt amount which encumbers real estate owned based upon book value	$2,300,000,000
Percentage of secured debt which encumbers real estate owned based upon book value	26.70%
Secured debt amount of real estate owned which is unencumbered	6,200,000,000
Percentage of secured debt of real estate owned which is unencumbered	73.30%
Weighted average interest rate	3.62%
Unamortized fair market adjustment	7,000,000			6,700,000
Borrowings outstanding	1,500,000			1,900,000
Extension period of option on loan	6 months
Line of Credit Facility, Interest Rate Description	100
Line of Credit Facility, Commitment Fee Description	15
Fixed Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Secured debt including debt on real estate held for sale	978,440,000			969,296,000
Weighted average interest rate	5.28%
Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Secured debt including debt on real estate held for sale	392,233,000			392,233,000
Weighted average interest rate	1.44%
3.75 MTN Due July 2024 [Member]
Secured Debt (Textual) [Abstract]
Weighted average interest rate	3.75%
Unamortized fair market adjustment	964,000			990,000
Debt Instrument, Maturity Date		1-Jul-24
Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Weighted average interest rate	5.49%
Debt Instrument, Maturity Date Range, Start	9-Dec-15
Debt instrument, maturity date range, end	1-May-19
Notes payable minimum interest rates range	3.43%
Notes payable maximum interest rates range	6.16%
Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Weighted average interest rate	1.94%
Debt Assumed As Part of Acquisition [Member]
Secured Debt (Textual) [Abstract]
Amortization of Debt Discount (Premium)	1,100,000		1,300,000
Tax Exempt Notes Payable [Member] \| Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Weighted average interest rate	0.76%
Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Debt, Weighted Average Interest Rate	5.12%
Debt Instrument, Maturity Date Range, Start	1-May-17
Debt instrument, maturity date range, end	1-Jul-23
Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Debt Instrument, Interest Rate at Period End	1.62%
Tax Exempt Secured Notes Payable [Member] \| Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Debt Instrument, Maturity Date Range, Start	1-Aug-19
Debt instrument, maturity date range, end	20-Mar-32
Notes payable minimum interest rates range	0.76%
Notes payable maximum interest rates range	0.77%
Fannie Mae [Member]
Secured Debt (Textual) [Abstract]
Borrowings outstanding	833,365,000			834,282,000
1.67% Term Notes due December 2016 [Member]
Secured Debt (Textual) [Abstract]
Weighted average interest rate	1.32%
Debt Instrument, Maturity Date	1-Jun-18
UDR Bank Credit Facility [Member]
Secured Debt (Textual) [Abstract]
Credit facilities with aggregate commitment	900,000,000			900,000,000
Increment in Unsecured Revolving Credit Facility Under Certain Circumstances	1,450,000,000
Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Secured debt including debt on real estate held for sale	567,169,000			568,086,000
Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Secured debt including debt on real estate held for sale	266,196,000			266,196,000
Mortgages Notes Payable [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Secured debt including debt on real estate held for sale	411,271,000			401,210,000
Mortgages Notes Payable [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Mortgages Notes Payable [Member] \| Variable Rate Debt [Member]
Secured Debt (Textual) [Abstract]
Secured debt including debt on real estate held for sale	$31,337,000			$31,337,000

Secured_and_Unsecured_Debt_Det7

Secured and Unsecured Debt (Details Textual 1) (USD $)	0 Months Ended	3 Months Ended
Secured and Unsecured Debt (Details Textual 1) (USD $)	Sep. 26, 2013	Mar. 31, 2015	Dec. 31, 2014
Unsecured Debt (Textual) [Abstract]
Credit facility interest rate		100
Line of Credit Facility, Commitment Fee Description		15
Line of Credit Facility, Amount Outstanding		$1,500,000	$1,900,000
Unamortized discount		7,000,000	6,700,000
Debt Instrument, Interest Rate During Period		3.62%
ThreePointSevenTermNotesDueOctober2020 [Member]
Unsecured Debt (Textual) [Abstract]
Debt Instrument, Maturity Date	31-Oct-20
Senior Notes		299,956,000	299,954,000
Debt Instrument, Interest Rate During Period		3.70%
1.67% Term Notes due December 2016 [Member]
Unsecured Debt (Textual) [Abstract]
Debt Instrument, Maturity Date		1-Jun-18
Senior Notes		35,000,000	35,000,000
Debt Instrument, Interest Rate During Period		1.32%
2.90% Term Notes due January 2016 [Member]
Unsecured Debt (Textual) [Abstract]
Senior Notes		215,000,000	215,000,000
Debt Instrument, Interest Rate During Period		1.70%
4.63% Medium-Term Notes due January 2022 [Member]
Unsecured Debt (Textual) [Abstract]
Unamortized discount		2,433,000	2,523,000
Senior Notes		397,567,000	397,477,000
Debt Instrument, Interest Rate During Period		4.63%
2.68% Term Notes due December 2016 [Member]
Unsecured Debt (Textual) [Abstract]
Senior Notes		100,000,000	100,000,000
Debt Instrument, Interest Rate During Period		1.53%
UDR Bank Credit Facility [Member]
Unsecured Debt (Textual) [Abstract]
Total revolving credit facility		900,000,000	900,000,000
Increase in maximum borrowing capacity of unsecured revolving credit facility		$1,450,000,000
Interest rate		1.10%	1.10%

Debt_UNITED_DOMINION_REALTY_LP2

Debt (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Weighted average interest rate	3.62%
Debt Instrument Weighted Average Years to Maturity	4 years 4 months 9 days
Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	$978,440	$969,296
Weighted average interest rate	5.28%
Debt Instrument Weighted Average Years to Maturity	2 years 9 months 10 days
Number of Communities Encumbered (in communities)	29
Fixed Rate Debt [Member] \| Mortgages Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate	5.49%
Debt Instrument Weighted Average Years to Maturity	1 year 4 months 20 days
Number of Communities Encumbered (in communities)	7
Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	3 years 9 months 10 days
Number of Communities Encumbered (in communities)	22
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	392,233	392,233
Weighted average interest rate	1.44%
Debt Instrument Weighted Average Years to Maturity	5 years 4 months 24 days
Number of Communities Encumbered (in communities)	10
Variable Rate Debt [Member] \| Mortgages Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.94%
Debt Instrument Weighted Average Years to Maturity	1 year 9 months 25 days
Number of Communities Encumbered (in communities)	1
Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	4 years 11 months 8 days
Number of Communities Encumbered (in communities)	7
Variable Rate Debt [Member] \| Tax Exempt Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate	0.76%
Debt Instrument Weighted Average Years to Maturity	7 years 11 months 8 days
Number of Communities Encumbered (in communities)	2
United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Principal outstanding	929,702	931,959
Weighted average interest rate	4.38%
Debt Instrument Weighted Average Years to Maturity	3 years 9 months 10 days
Number of Communities Encumbered (in communities)	21
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	709,942	712,199
Weighted average interest rate	5.21%
Debt Instrument Weighted Average Years to Maturity	2 years 9 months
Number of Communities Encumbered (in communities)	15
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member] \| Mortgages Notes Payable [Member]
Debt Instrument [Line Items]
Principal outstanding	376,207	378,371
Weighted average interest rate	5.48%
Debt Instrument Weighted Average Years to Maturity	1 year 4 months 7 days
Number of Communities Encumbered (in communities)	5
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.90%
Debt Instrument Weighted Average Years to Maturity	4 years 3 months 25 days
Number of Communities Encumbered (in communities)	10
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Principal outstanding	219,760	219,760
Weighted average interest rate	1.72%
Debt Instrument Weighted Average Years to Maturity	7 years 1 month 13 days
Number of Communities Encumbered (in communities)	6
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.85%
Debt Instrument Weighted Average Years to Maturity	5 years 8 months 26 days
Number of Communities Encumbered (in communities)	5
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member] \| Tax Exempt Notes Payable [Member]
Debt Instrument [Line Items]
Principal outstanding	27,000	27,000
Weighted average interest rate	0.77%
Debt Instrument Weighted Average Years to Maturity	16 years 11 months 19 days
Number of Communities Encumbered (in communities)	1
Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	567,169	568,086
Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	266,196	266,196
Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	333,735	333,828
Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member] \| United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member] \| Fannie Mae credit facilities [Member]
Debt Instrument [Line Items]
Principal outstanding	$192,760	$192,760

Debt_UNITED_DOMINION_REALTY_LP3

Debt (UNITED DOMINION REALTY, L.P.) (Details 1) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2013	Dec. 31, 2014
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	4 years 4 months 9 days
Borrowings outstanding	$1,500		$1,900
Fannie Mae [Member]
Debt Instrument [Line Items]
Borrowings outstanding	833,365		834,282
Weighted average daily borrowings during the period ended	833,697	835,873
Maximum daily borrowings during the period ended	834,003	837,564
Weighted average interest rate during the period ended	4.00%	4.10%
Interest rate at the end of the period	4.00%		4.00%
United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	3 years 9 months 10 days
United Dominion Reality L.P. [Member] \| Fannie Mae [Member]
Debt Instrument [Line Items]
Borrowings outstanding	526,495		526,588
Weighted average daily borrowings during the period ended	526,705	527,592
Maximum daily borrowings during the period ended	$526,898	$528,659
Weighted average interest rate during the period ended	4.00%	4.10%
Interest rate at the end of the period	4.00%		4.00%
Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	2 years 9 months 10 days
Fixed Rate Debt [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	1 year 4 months 20 days
Fixed Rate Debt [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	3 years 9 months 10 days
Fixed Rate Debt [Member] \| United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	2 years 9 months
Fixed Rate Debt [Member] \| United Dominion Reality L.P. [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	1 year 4 months 7 days
Fixed Rate Debt [Member] \| United Dominion Reality L.P. [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	4 years 3 months 25 days
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	5 years 4 months 24 days
Variable Rate Debt [Member] \| Mortgages [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	1 year 9 months 25 days
Variable Rate Debt [Member] \| Tax Exempt Notes Payable [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	7 years 11 months 8 days
Variable Rate Debt [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	4 years 11 months 8 days
Variable Rate Debt [Member] \| United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	7 years 1 month 13 days
Variable Rate Debt [Member] \| United Dominion Reality L.P. [Member] \| Tax Exempt Notes Payable [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	16 years 11 months 19 days
Variable Rate Debt [Member] \| United Dominion Reality L.P. [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument Weighted Average Years to Maturity	5 years 8 months 26 days

Debt_UNITED_DOMINION_REALTY_LP4

Debt (UNITED DOMINION REALTY, L.P.) (Details 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
2014	$194,893
2015	242,691
2016	663,219
2017	874,916
2018	313,571
Thereafter	1,227,379
Total	1,370,673	1,361,529
United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
2014	190,856
2015	131,406
2016	23,119
2017	208,994
2018	175,818
Thereafter	199,509
Total	929,702	931,959
United Dominion Reality L.P. [Member] \| Mortgages Notes Payable [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
2014	190,582
2015	131,021
2016	913
2017	968
2018	52,723
Thereafter	0
Total	376,207
United Dominion Reality L.P. [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
2014	274
2015	385
2016	15,640
2017	111,052
2018	123,095
Thereafter	83,289
Total	333,735
United Dominion Reality L.P. [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
2014	0
2015	0
2016	6,566
2017	96,974
2018	0
Thereafter	89,220
Total	192,760
United Dominion Reality L.P. [Member] \| Tax Exempt Notes Payable [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
2014	0
2015	0
2016	0
2017	0
2018	0
Thereafter	27,000
Total	$27,000

Debt_UNITED_DOMINION_REALTY_LP5

Debt (UNITED DOMINION REALTY, L.P.) (Details Textual) (USD $)	3 Months Ended	0 Months Ended
	Mar. 31, 2015	Sep. 26, 2013	Jun. 27, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Borrowings outstanding	$1,500,000			$1,900,000
Weighted average interest rate	3.62%
Unamortized fair market adjustment	7,000,000			6,700,000
UDR Bank Credit Facility [Member]
Debt Instrument [Line Items]
Total revolving credit facility	900,000,000			900,000,000
Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	978,440,000			969,296,000
Weighted average interest rate	5.28%
Variable Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	392,233,000			392,233,000
Weighted average interest rate	1.44%
Fannie Mae [Member]
Debt Instrument [Line Items]
Borrowings outstanding	833,365,000			834,282,000
Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	1-May-17
Debt Instrument, Maturity Date Range, End	1-Jul-23
Debt, Weighted Average Interest Rate	5.12%
Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate at Period End	1.62%
Mortgages [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, Start	9-Dec-15
Weighted average interest rate	5.49%
Notes payable minimum interest rates range	3.43%
Notes payable maximum interest rates range	6.16%
Debt Instrument, Maturity Date Range, End	1-May-19
Mortgages [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.94%
Tax Exempt Notes Payable [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate	0.76%
Unsecured Revolving Credit Facility due October 2015 [Member]
Debt Instrument [Line Items]
Borrowings outstanding	389,000,000			152,500,000
Weighted average interest rate	1.08%
2.90% Term Notes due January 2016 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.70%
Five Point Two Five Percent, Medium Term Notes, Due January 2016 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	5.25%
4.25% Medium-Term Notes due June 2018 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.25%
Unamortized fair market adjustment	1,358,000			1,465,000
Three point seven percent medium term note due October 2020 [Member]
Debt Instrument [Line Items]
Unamortized fair market adjustment	44,000			46,000
ThreePointSevenTermNotesDueOctober2020 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	3.70%
Debt Instrument, Maturity Date		31-Oct-20
4.63% Medium-Term Notes due January 2022 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.63%
Unamortized fair market adjustment	2,433,000			2,523,000
3.75 MTN Due July 2024 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	3.75%
Unamortized fair market adjustment	964,000			990,000
Debt Instrument, Maturity Date			1-Jul-24
United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Premium	5,200,000			6,200,000
Secured debt including debt on real estate held for sale	929,702,000			931,959,000
Weighted average interest rate	4.38%
United Dominion Reality L.P. [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	709,942,000			712,199,000
Weighted average interest rate	5.21%
United Dominion Reality L.P. [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	219,760,000			219,760,000
Weighted average interest rate	1.72%
United Dominion Reality L.P. [Member] \| Fannie Mae [Member]
Debt Instrument [Line Items]
Borrowings outstanding	526,495,000			526,588,000
United Dominion Reality L.P. [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.90%
United Dominion Reality L.P. [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate	1.85%
United Dominion Reality L.P. [Member] \| Mortgages [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	376,207,000			378,371,000
Weighted average interest rate	5.48%
Notes payable maximum interest rates range	5.94%
United Dominion Reality L.P. [Member] \| Tax Exempt Notes Payable [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	27,000,000			27,000,000
Weighted average interest rate	0.77%
Debt Instrument, Maturity Date Range, End	1-Mar-32
United Dominion Reality L.P. [Member] \| 2.90% Term Notes due January 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End	6-Jun-18
United Dominion Reality L.P. [Member] \| 2.90% Term Notes due January 2016 [Member] \| Financial Guarantee [Member]
Debt Instrument [Line Items]
Guarantor borrowing capacity	250,000,000
United Dominion Reality L.P. [Member] \| 1.68% Term Notes due December 2016 [Member] \| Financial Guarantee [Member]
Debt Instrument [Line Items]
Guarantor borrowing capacity	100,000,000
United Dominion Reality L.P. [Member] \| Five Point Two Five Percent, Medium Term Notes, Due January 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End	6-Jun-18
United Dominion Reality L.P. [Member] \| 4.25% Medium-Term Notes due June 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End	1-Jun-18
United Dominion Reality L.P. [Member] \| 4.25% Medium-Term Notes due June 2018 [Member] \| Financial Guarantee [Member]
Debt Instrument [Line Items]
Guarantor borrowing capacity	300,000,000
United Dominion Reality L.P. [Member] \| Three point seven percent medium term note due October 2020 [Member] \| Financial Guarantee [Member]
Debt Instrument [Line Items]
Guarantor borrowing capacity	300,000,000
United Dominion Reality L.P. [Member] \| 4.63% Medium-Term Notes due January 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End	1-Jan-22
United Dominion Reality L.P. [Member] \| 4.63% Medium-Term Notes due January 2022 [Member] \| Financial Guarantee [Member]
Debt Instrument [Line Items]
Guarantor borrowing capacity	400,000,000
United Dominion Reality L.P. [Member] \| 3.75 MTN Due July 2024 [Member] \| Financial Guarantee [Member]
Debt Instrument [Line Items]
Guarantor borrowing capacity	300,000,000
Mortgages [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	411,271,000			401,210,000
Mortgages [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	31,337,000			31,337,000
Mortgages [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Fixed Rate Secured Debt Instruments Fair Value	376,207,000			378,371,000
Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	567,169,000			568,086,000
Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	266,196,000			266,196,000
Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member]
Debt Instrument [Line Items]
Variable Rate Secured Debt Instruments Fair Value	192,760,000			192,760,000
Fixed Rate Secured Debt Instruments Fair Value	333,735,000			333,828,000
Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Fannie Mae credit facilities [Member] \| Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	333,735,000			333,828,000
Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Fannie Mae credit facilities [Member] \| Variable Rate Debt [Member]
Debt Instrument [Line Items]
Secured debt including debt on real estate held for sale	$192,760,000			$192,760,000

IncomeLoss_Per_Share_Details

Income/(Loss) Per Share (Details) (USD $)	3 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Income/(loss) from continuing operations	$76,417,000	($5,195,000)
Gains/(loss) on sales of real estate, net of tax	0	24,294,000
(Income)/loss from continuing operations attributable to noncontrolling interest	-2,588,000
Income/(loss) from continuing operations attributable to UDR, Inc.	73,822,000	18,445,000
Income/(loss) from continuing operations operations attributable to common stockholders	72,891,000	17,514,000
Income/(loss) from discontinued operations, net of tax	0	-87,000
(Income)/loss from discontinued operations attributable to redeemable noncontrolling interest in the Operating Partnership	0	3,000
Income/(loss) from discontinued operations attributable to common stockholders	0	-84,000
Net income/(loss)	76,417,000	19,012,000
Net (income)/loss attributable to noncontrolling interests	-7,000	-4,000
Net (income)/loss attributable to redeemable non-controlling interests in Operating Partnership	2,588,000	647,000
Net (loss)/income attributable to common stockholders	72,891,000	17,430,000
Denominator for earnings per share - basic and diluted:
Weighted average common shares outstanding	258,100	251,213
Non-vested restricted stock rewards	-1,266,000	-1,036,000
Weighted average number of common shares outstanding b basic	256,834	250,177
Incremental shares issuable for assumed conversion of: Stock options and unvested restricted stock	-1,828	-1,645
Weighted average number of common shares outstanding b diluted	258,662	251,822
Income/(loss) from continuing operations attributable to common stockholders	$0.28	$0.07
Net income/(loss) attributable to common stockholders	$0.28	$0.07
Income/(loss) from discontinued operations attributable to common stockholders,	$0	$0
Income/(loss) from continuing operations attributable to common stockholders,	$0.28	$0.07
Income from discontinued operations attributable to common stockholders	$0	$0
Net income/(loss) attributable to common stockholders	$0.28	$0.07
OP Units [Member]
Denominator for earnings per share - basic and diluted:
Antidilutive securities	9,165		9,319
Convertible Preferred Stock [Member]
Denominator for earnings per share - basic and diluted:
Antidilutive securities	3,036		3,036
Stock options and unvested restricted stock [Member]
Denominator for earnings per share - basic and diluted:
Antidilutive securities	1,828		1,645
Series E Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Distributions to preferred stockholders - Series E (Convertible)	931,000	931,000
RedeemableNoncontrollingInterest [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
(Income)/loss from continuing operations attributable to noncontrolling interest		($650,000)

Noncontrolling_Interests_Detai

Noncontrolling Interests (Details) (USD $)	3 Months Ended
Noncontrolling Interests (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Redeemable noncontrolling interests in the Operating Partnership	$311,883,000			$282,480,000
Net Income (Loss) Available to Common Stockholders, Basic	72,891,000	17,430,000
Change in equity from net income(loss) attributable to common stockholders and conversion of OP Units to UDR Common Stock	72,908,000		17,430,000
Redeemable noncontrolling interests in the Operating Partnership
Mark to market adjustment to redeemable noncontrolling interests in the Operating Partnership	29,696,000
Adjustment for conversion of noncontrolling interest of unitholders in Operating Partnership	17,000		0
Net (income)/loss attributable to redeemable non-controlling interests in Operating Partnership	2,588,000	647,000
Distributions to redeemable noncontrolling interests in the Operating Partnership	2,639,000
Redeemable non-controlling interests in operating partnership	311,883,000
Net income attributable to non-controlling interests	$7,000	$4,000

Related_Party_Transactions_UNI1

Related Party Transactions (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Related Party Transaction [Line Items]
Related party management fees	$4,300,000	$3,100,000
United Dominion Reality L.P. [Member]
Related Party Transaction [Line Items]
Limited partnership units owned	183,167,815		183,167,815
Net receivable balances from General Partner	22,418,000		13,624,000
Related Party Transaction, Management Fee Percentage	2.75%
Interest Expense, Related Party	1,151,000	1,151,000
Notes payable due to General Partner	88,696,000		88,696,000
United Dominion Reality L.P. [Member] \| Taxable REIT Subsidiaries [Member]
Related Party Transaction [Line Items]
Net receivable balances from General Partner	-22,418,000		-13,624,000
Related Party Transaction, Management Fee Percentage	2.75%
United Dominion Reality L.P. [Member] \| UDR, Inc. [Member]
Related Party Transaction [Line Items]
General and administrative expenses allocated to the Operating Partnership by UDR	4,200,000	6,700,000
United Dominion Reality L.P. [Member] \| UDR, Inc. [Member] \| Bottom Dollar Guaranty [Member]
Related Party Transaction [Line Items]
Notes payable due to General Partner			$88,700,000
Note for 83.2 million [Member] \| United Dominion Reality L.P. [Member] \| UDR, Inc. [Member] \| Guaranty Related To Community Acquisition [Member]
Related Party Transaction [Line Items]
Related party guaranty note payable interest rate	5.18%
Debt Instrument, Maturity Date Range, End	31-Aug-21
Note for 5 million [Member] \| United Dominion Reality L.P. [Member] \| UDR, Inc. [Member] \| Guaranty Related To Community Acquisition [Member]
Related Party Transaction [Line Items]
Related party guaranty note payable interest rate	5.34%
Debt Instrument, Maturity Date Range, End	31-Dec-23

Fair_Value_of_Derivatives_and_4

Fair Value of Derivatives and Financial Instruments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes receivable, net	$15,494	$14,369
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	0
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Asset	29	88
Derivative Liability	17,112	10,368
Secured debt instruments - variable rate
Borrowings outstanding	1,500	1,900
Unsecured debt instruments
Redeemable Noncontrolling Interest, Equity, Carrying Amount	311,883
Redeemable noncontrolling interests in the Operating Partnership (d)	311,883	282,480
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes receivable, net	15,494	14,369
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	15,523	14,457
Unsecured debt instruments
Total liabilities	3,533,781	3,593,473
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivative Liability	17,112	10,368
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Senior Unsecured Notes [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	1,756,996	2,069,076
Estimate of Fair Value, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Notes receivable (a)	15,923	14,808
Total assets	15,952	14,896
Unsecured debt instruments
Total liabilities	3,676,255	3,721,512
Redeemable noncontrolling interests in the Operating Partnership (d)	311,883	282,480
Estimate of Fair Value, Fair Value Disclosure [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	29	88
Derivatives - Interest rate contracts (b)	17,112	10,368
Estimate of Fair Value, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	425,969	415,663
Secured debt instruments - variable rate
Secured debt instruments - variable rate	31,337	31,337
Estimate of Fair Value, Fair Value Disclosure [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	94,700	94,700
Estimate of Fair Value, Fair Value Disclosure [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	599,580	606,623
Secured debt instruments - variable rate
Secured debt instruments - variable rate	266,196	266,196
Unsecured debt instruments
Unsecured debt instruments (c)		152,500
Estimate of Fair Value, Fair Value Disclosure [Member] \| Senior Unsecured Notes [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	1,852,361	2,144,125
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Notes receivable (a)	0	0
Total assets	0	0
Unsecured debt instruments
Total liabilities	0	0
Redeemable noncontrolling interests in the Operating Partnership (d)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	0	0
Derivatives - Interest rate contracts (b)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Commercial bank [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Senior Unsecured Notes [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Notes receivable (a)	0	0
Total assets	29	88
Unsecured debt instruments
Total liabilities	17,112	10,368
Redeemable noncontrolling interests in the Operating Partnership (d)	311,883	282,480
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	29	88
Derivatives - Interest rate contracts (b)	17,112	10,368
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Commercial bank [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Senior Unsecured Notes [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Notes receivable (a)	15,923	14,808
Total assets	15,923	14,808
Unsecured debt instruments
Total liabilities	3,659,143	3,711,144
Redeemable noncontrolling interests in the Operating Partnership (d)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	0	0
Derivatives - Interest rate contracts (b)	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	425,969	415,663
Secured debt instruments - variable rate
Secured debt instruments - variable rate	31,337	31,337
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	94,700	94,700
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	599,580	606,623
Secured debt instruments - variable rate
Secured debt instruments - variable rate	266,196	266,196
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Commercial bank [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	389,000	152,500
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Senior Unsecured Notes [Member] \| Fair Value, Measurements, Recurring [Member]
Unsecured debt instruments
Unsecured debt instruments (c)	1,852,361	2,144,125
Unsecured Revolving Credit Facility due October 2015 [Member]
Secured debt instruments - variable rate
Borrowings outstanding	389,000	152,500
Variable Rate Debt [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	392,233	392,233
Variable Rate Debt [Member] \| Tax Exempt Notes Payable [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	94,700	94,700
Variable Rate Debt [Member] \| Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	266,196	266,196
Variable Rate Debt [Member] \| Mortgages Notes Payable [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	31,337	31,337
Fixed Rate Debt [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	978,440	969,296
Fixed Rate Debt [Member] \| Line of Credit [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	567,169	568,086
Fixed Rate Debt [Member] \| Mortgages Notes Payable [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Secured debt including debt on real estate held for sale	$411,271	$401,210

Fair_Value_of_Derivatives_and_5

Fair Value of Derivatives and Financial Instruments (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
United Dominion Reality L.P. [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	$17	$39
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
Estimate of Fair Value, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	15,952	14,896
Secured debt instruments - variable rate
Total liabilities	3,676,255	3,721,512
Estimate of Fair Value, Fair Value Disclosure [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	29	88
Derivative Liability Designated as Hedging Instrument, Fair Value	17,112	10,368
Estimate of Fair Value, Fair Value Disclosure [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	425,969	415,663
Secured debt instruments - variable rate
Secured debt instruments - variable rate	31,337	31,337
Estimate of Fair Value, Fair Value Disclosure [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	94,700	94,700
Estimate of Fair Value, Fair Value Disclosure [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	599,580	606,623
Secured debt instruments - variable rate
Secured debt instruments - variable rate	266,196	266,196
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	0	0
Secured debt instruments - variable rate
Total liabilities	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	0	0
Derivative Liability Designated as Hedging Instrument, Fair Value	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 1 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	29	88
Secured debt instruments - variable rate
Total liabilities	17,112	10,368
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	29	88
Derivative Liability Designated as Hedging Instrument, Fair Value	17,112	10,368
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 2 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	15,923	14,808
Secured debt instruments - variable rate
Total liabilities	3,659,143	3,711,144
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	0	0
Derivative Liability Designated as Hedging Instrument, Fair Value	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	425,969	415,663
Secured debt instruments - variable rate
Secured debt instruments - variable rate	31,337	31,337
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	94,700	94,700
Estimate of Fair Value, Fair Value Disclosure [Member] \| Level 3 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	599,580	606,623
Secured debt instruments - variable rate
Secured debt instruments - variable rate	266,196	266,196
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	17	39
Secured debt instruments - variable rate
Total liabilities	962,032	967,983
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	17	39
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	388,821	391,835
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	27,000	27,000
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	352,765	355,470
Secured debt instruments - variable rate
Secured debt instruments - variable rate	192,760	192,760
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	0	0
Secured debt instruments - variable rate
Total liabilities	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 1 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	0	0
Derivative Liability Designated as Hedging Instrument, Fair Value	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 1 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 1 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 1 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	17	39
Secured debt instruments - variable rate
Total liabilities	686	918
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 2 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	17	39
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 2 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 2 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 2 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	0	0
Secured debt instruments - variable rate
Secured debt instruments - variable rate	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	0	0
Secured debt instruments - variable rate
Total liabilities	961,346	967,065
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 3 [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	0	0
Derivative Liability Designated as Hedging Instrument, Fair Value	0	0
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 3 [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	388,821	391,835
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 3 [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	27,000	27,000
Estimate of Fair Value, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Level 3 [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	352,765	355,470
Secured debt instruments - variable rate
Secured debt instruments - variable rate	192,760	192,760
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	15,523	14,457
Secured debt instruments - variable rate
Total liabilities	3,533,781	3,593,473
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Total assets	17	39
Secured debt instruments - variable rate
Total liabilities	930,388	932,877
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Interest Rate Contracts [Member] \| Fair Value, Measurements, Recurring [Member]
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis
Derivatives - Interest rate contracts	17	39
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Mortgages Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	376,207	378,371
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Tax Exempt Notes Payable [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - variable rate
Secured debt instruments - variable rate	27,000	27,000
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| United Dominion Reality L.P. [Member] \| Line of Credit [Member] \| Fair Value, Measurements, Recurring [Member]
Secured debt instruments - fixed rate
Secured debt instruments - fixed rate	333,735	333,828
Secured debt instruments - variable rate
Secured debt instruments - variable rate	$192,760	$192,760

Derivatives_and_Hedging_Activi4

Derivatives and Hedging Activity (Details) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified	Mar. 31, 2015
Designated as Hedging Instrument [Member] \| Interest rate swaps [Member]
Derivative [Line Items]
Number instruments	9
Notional	$565,000
Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivative [Line Items]
Number instruments	3
Notional	243,079
Not Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivative [Line Items]
Number instruments	1
Notional	$96,409

Derivatives_and_Hedging_Activi5

Derivatives and Hedging Activity (Details 1) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Interest Rate Products [Member] \| Other Assets [Member] \| Designated as Hedging Instrument [Member]
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Derivative Asset Designated as Hedging Instrument, Fair Value	$28	$86
Interest Rate Products [Member] \| Other Assets [Member] \| Not Designated as Hedging Instrument [Member]
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Derivative Asset Not Designated as Hedging Instrument, Fair Value	1	2
Interest Rate Products [Member] \| Other Liabilities [Member] \| Designated as Hedging Instrument [Member]
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Derivative Liability Designated as Hedging Instrument, Fair Value	17,112	10,368
Interest Rate Products [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instrument [Member]
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Derivative Liability Not Designated as Hedging Instrument, Fair Value	0	0
Interest rate caps [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held	3
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Notional	243,079
Interest rate caps [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held	1
Fair value of Company's derivative financial instruments and their classification on Consolidated Balance Sheet
Notional	$96,409

Derivatives_and_Hedging_Activi6

Derivatives and Hedging Activity (Details 2) (USD $)	3 Months Ended
Derivatives and Hedging Activity (Details 2) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Effect of derivative instruments on the Consolidated Statements of Operations
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$737,000	$1,532,000
Unrealized holding gain/(loss)	-7,552,000	-55,000
Amount of Gain or (Loss) Recognized in Income on Derivative	-1,000		0
Interest Rate Products [Member] \| Interest Expense [Member] \| Cash Flow Hedging [Member]
Effect of derivative instruments on the Consolidated Statements of Operations
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	-737,000		-1,532,000
Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	$0		$0

Derivatives_and_Hedging_Activi7

Derivatives and Hedging Activity (Details 3) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Offsetting Derivative Assets [Abstract]
Gross Amounts Offset in the Consolidated Balance Sheets	$0	$0
Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)	29	88
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	-27
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	29	61
Offsetting Derivative Liabilities [Abstract]
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)	17,112	10,368
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	-27
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	17,112	10,341
Fair Value, Measurements, Recurring [Member] \| Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Interest Rate Contracts [Member]
Offsetting Derivative Liabilities [Abstract]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)	$17,112	$10,368

Derivatives_and_Hedging_Activi8

Derivatives and Hedging Activity (Details Textual) (USD $)	3 Months Ended
Derivatives and Hedging Activity (Details Textual) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Obligation to Return Cash	$0			$0
Derivatives And Hedging Activity (Textual) [Abstract]
Cash flow hedge ineffectiveness in earnings materiality	0	0
Estimated additional accumulated other comprehensive Income/(Loss) transferred to interest expense	6,300,000
Derivative instruments not designated as hedging instruments, gain (loss), net	-1,000		0
Payment required to pay for contract termination	17,500,000
Other Income Expense [Member] \| Interest Rate Contracts [Member]
Derivatives And Hedging Activity (Textual) [Abstract]
Derivative instruments not designated as hedging instruments, gain (loss), net	$0	0

Derivatives_and_Hedging_Activi9

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified	Mar. 31, 2015
Designated as Hedging Instrument [Member] \| Interest rate swaps [Member]
Derivative [Line Items]
Number instruments	9
Notional	$565,000
Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivative [Line Items]
Number instruments	3
Notional	243,079
Not Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivative [Line Items]
Number instruments	1
Notional	96,409
United Dominion Reality L.P. [Member] \| Designated as Hedging Instrument [Member] \| Interest rate swaps [Member]
Derivative [Line Items]
Number instruments	1
Notional	46,272
United Dominion Reality L.P. [Member] \| Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivative [Line Items]
Number instruments	2
Notional	166,341
United Dominion Reality L.P. [Member] \| Not Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivative [Line Items]
Number instruments	1
Notional	$89,220

Recovered_Sheet1

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Details 1) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Interest Rate Products [Member] \| Other Assets [Member] \| Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset Designated as Hedging Instrument, Fair Value	$28	$86
Interest Rate Products [Member] \| Other Assets [Member] \| Not Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset Not Designated as Hedging Instrument, Fair Value	1	2
Interest Rate Products [Member] \| Other Liabilities [Member] \| Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Liability Designated as Hedging Instrument, Fair Value	17,112	10,368
Interest Rate Products [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Liability Not Designated as Hedging Instrument, Fair Value	0	0
United Dominion Reality L.P. [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset Designated as Hedging Instrument, Fair Value	17	39
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
United Dominion Reality L.P. [Member] \| Interest Rate Products [Member] \| Other Assets [Member] \| Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset Designated as Hedging Instrument, Fair Value	16	37
United Dominion Reality L.P. [Member] \| Interest Rate Products [Member] \| Other Assets [Member] \| Not Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Asset Not Designated as Hedging Instrument, Fair Value	1	2
United Dominion Reality L.P. [Member] \| Interest Rate Products [Member] \| Other Liabilities [Member] \| Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
United Dominion Reality L.P. [Member] \| Interest Rate Products [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instrument [Member]
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Derivative Liability Not Designated as Hedging Instrument, Fair Value	$0	$0

Recovered_Sheet2

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$737,000	$1,532,000
Amount of Gain or (Loss) Recognized in Income on Derivative	-1,000		0
Interest Rate Products [Member] \| Other Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	0	0
Interest Rate Products [Member] \| Interest Expense [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	-737,000		-1,532,000
United Dominion Reality L.P. [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)	-51,000	-51,000
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	286,000	623,000
Amount of Gain or (Loss) Recognized in Income on Derivative	0	0
United Dominion Reality L.P. [Member] \| Interest Rate Products [Member] \| Other Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	-1,000		0
United Dominion Reality L.P. [Member] \| Interest Rate Products [Member] \| Interest Expense [Member] \| Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	($286,000)		($623,000)

Recovered_Sheet3

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Details 3) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Offsetting Derivative Assets [Abstract]
Gross Amounts Offset in the Consolidated Balance Sheets	$0	$0
Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)	29	88
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	27
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	29	61
Offsetting Derivative Liabilities [Abstract]
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)	17,112	10,368
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	27
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	17,112	10,341
United Dominion Reality L.P. [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset Designated as Hedging Instrument, Fair Value	17	39
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets (a)	17	39
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	17	39
Offsetting Derivative Liabilities [Abstract]
Derivative Liability Designated as Hedging Instrument, Fair Value	686	918
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheets (b)	686	918
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	$686	$918

Recovered_Sheet4

Derivatives and Hedging Activity (UNITED DOMINION REALTY, L.P.) (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014
Entity Information [Line Items]
Cash flow hedge ineffectiveness in earnings materiality	0	0
Estimated additional accumulated other comprehensive Income/(Loss) transferred to interest expense	$6,300,000
Losses in the fair value of derivatives not designated in hedging relationships	1,000		0
Payment required to pay for contract termination	17,500,000
Derivative, Collateral, Obligation to Return Cash	0			0
United Dominion Reality L.P. [Member]
Entity Information [Line Items]
Cash flow hedge ineffectiveness in earnings materiality	0	0
Estimated additional accumulated other comprehensive Income/(Loss) transferred to interest expense	691,000
Losses in the fair value of derivatives not designated in hedging relationships	0	0
Fair value of derivatives in a net liability position	774,000
Derivative, Collateral, Obligation to Return Cash	$0			$0

Stock_Based_Compensation_Detai

Stock Based Compensation (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Stock Based Compensation (Textual) [Abstract]
Stock based compensation expense	$4.50	$3.70

Capital_Structure_UNITED_DOMIN1

Capital Structure (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Limited Partners' Capital Account [Line Items]
Redeemable noncontrolling interests in the Operating Partnership	311,883	282,480
United Dominion Reality L.P. [Member]
Limited Partners' Capital Account [Line Items]
General Partnership units outstanding	110,883	110,883
Limited partnership units owned	183,167,815	183,167,815
Limited Partners' Capital Account, Required Period To Be Outstanding Before Unit is Redeemable	1 year
UDR, Inc. [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	174,002,876	174,002,342
Percentage of units	95.00%	95.00%
Non-affiliated Partners [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	9,164,939	9,165,473
Percentage of units	5.00%	5.00%
Class A Limited Partner [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	1,751,671
Cumulative, annual, non-compounded preferred return on Class A Partnership units	8.00%
Value of Class A Partnership units (in dollars per unit)	16.61
Class A Limited Partner [Member] \| United Dominion Reality L.P. [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	1,873,332	1,873,332
Class A Limited Partner [Member] \| UDR, Inc. [Member]
Limited Partners' Capital Account [Line Items]
Limited partnership units owned	121,661

Commitments_and_Contingencies_2

Commitments and Contingencies (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Real Estate Properties [Line Items]
Number of communities owned (in communities)	138
Costs Incurred to Date	$648,412
Expected Costs to Complete	249,064
Wholly owned b under development [Member]
Real Estate Properties [Line Items]
Capital Expenditures Incurred but Not yet Paid	11,100
Number of communities owned (in communities)	1
Costs Incurred to Date	196,653
Expected Costs to Complete	21,047
Average Ownership Stake	100.00%
Wholly owned b redevelopment [Member]
Real Estate Properties [Line Items]
Capital Expenditures Incurred but Not yet Paid	2,300
Number of communities owned (in communities)	2
Costs Incurred to Date	90,382
Expected Costs to Complete	22,618
Average Ownership Stake	100.00%
Unconsolidated joint ventures [Member]
Real Estate Properties [Line Items]
Number of communities owned (in communities)	4
Costs Incurred to Date	285,730
Expected Costs to Complete	189,037
Participating Loan Investment Steele Creek Denver Colorado [Member]
Real Estate Properties [Line Items]
Costs Incurred to Date	75,647
Expected Costs to Complete	$16,362
Average Ownership Stake	0.00%

Commitments_and_Contingencies_3

Commitments and Contingencies (UNITED DOMINION REALTY, L.P.) Commitments and Contingencies (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Loss Contingencies [Line Items]
Number of communities owned (in communities)	138
Cost Incurred to Date	$648,412
United Dominion Reality L.P. [Member]
Loss Contingencies [Line Items]
Number of communities owned (in communities)	68
Wholly owned b redevelopment [Member]
Loss Contingencies [Line Items]
Capital Expenditures Incurred but Not yet Paid	2,300
Number of communities owned (in communities)	2
Cost Incurred to Date	90,382
Wholly owned b redevelopment [Member] \| United Dominion Reality L.P. [Member]
Loss Contingencies [Line Items]
Capital Expenditures Incurred but Not yet Paid	515
Number of communities owned (in communities)	1
Cost Incurred to Date	2,310
Expected Costs to Complete	12,690
Wholly owned b under development [Member]
Loss Contingencies [Line Items]
Capital Expenditures Incurred but Not yet Paid	11,100
Number of communities owned (in communities)	1
Cost Incurred to Date	$196,653

Reportable_Segments_Details

Reportable Segments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
	Segments	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Same Store Communities	36,063
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	$219,753	$198,039
Reportable apartment home segment NOI	143,575	132,124
Reconciling items:
Joint venture management and other fees	12,706	3,687
Property management	-5,694	-5,346
Other operating expenses	-1,766	-1,935
Real estate depreciation and amortization	88,777	88,533
Segment Reporting Reconciling Items Cost of Services Depreciation and Amortization	-88,777	-88,533
General and administrative	-12,152	-11,994
Casualty (Recoveries)/Charges	-996	-500
Casualty-related (recoveries)/charges, net	996	500
Other depreciation and amortization	-1,623	-1,080
Income/(loss) from unconsolidated entities	59,159	-3,565
Interest expense	28,800	-32,884
Interest and other income/(expense), net	360	1,415
Gains/(loss) on sales of real estate, net of tax	0	24,294
Tax benefit, net	425	3,329
Gain on sale of real estate owned, net of tax	0	24,294
Gain Loss on the Sale of Real Estate, Including Discontinued Operations	0
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership	-2,588	-647
Net (income)/loss attributable to noncontrolling interests	-7	-4
Net income/(loss) attributable to UDR, Inc.	73,822	18,361
Reportable apartment home segment assets:
Total segment assets	8,453,648			8,383,259
Accumulated depreciation	-2,522,100			-2,434,772
Total segment asset - net book value	5,931,548			5,948,487
Reconciling items:
Cash and cash equivalents	6,274	15,891		15,224	30,249
Restricted cash	23,266			22,340
Deferred financing costs, net	21,676			22,686
Notes receivable, net	15,494			14,369
Other assets	96,713			105,202
Total consolidated assets	6,858,511			6,846,534
Reportable Segment (Textual) [Abstract]
Number of reportable segments	2
Condition for Community considered to have stabilized occupancy	0.9
Number of Tenants or related group of tenants that contributed 10% or more of company total revenue	0	0
Same Communities [Member]
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	13,300	7,700
Same Store Communities Western Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	67,857	63,267
Reportable apartment home segment NOI	50,228	45,408
Reportable apartment home segment assets:
Total segment assets	2,626,770			2,620,242
Same Store Communities Mid-Atlantic Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	42,795	42,049
Reportable apartment home segment NOI	29,288	28,835
Reportable apartment home segment assets:
Total segment assets	1,536,389			1,533,993
Same Store Communities Northeast Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	20,892	19,803
Reportable apartment home segment NOI	15,566	14,546
Reportable apartment home segment assets:
Total segment assets	1,078,431			1,076,656
Same Store Communities Southeastern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	27,829	26,497
Reportable apartment home segment NOI	18,547	17,872
Reportable apartment home segment assets:
Total segment assets	788,668			786,438
Same Store Communities Southwestern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	14,107	13,467
Reportable apartment home segment NOI	8,536	8,358
Reportable apartment home segment assets:
Total segment assets	441,888			440,721
Non-Mature communities/Other [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	33,567	29,317
Reportable apartment home segment NOI	21,410	17,105
Reportable apartment home segment assets:
Total segment assets	1,981,502			1,925,209
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	2,500	2,100
Total Communities [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	207,047	194,400
Segment Reconciling Items [Member]
Reconciling items:
Gain Loss on the Sale of Real Estate, Including Discontinued Operations		24,294
United Dominion Reality L.P. [Member]
Segment Reporting Information [Line Items]
Same Store Communities	19,209
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment NOI	78,115		72,417
Reconciling items:
Property management	-3,027		-2,815
Other operating expenses	-1,490		-1,436
Real estate depreciation and amortization	44,478	44,271
General and administrative	-5,639		-6,970
Casualty (Recoveries)/Charges	-593	-500	500
Interest expense	-10,771		-10,014
Gains/(loss) on sales of real estate, net of tax	24,623	24,402
Net (income)/loss attributable to noncontrolling interests	-394		-280
Net income/(loss) attributable to UDR, Inc.	36,346	30,533	30,533
Reportable apartment home segment assets:
Total segment assets	4,248,795			4,238,770
Accumulated depreciation	-1,447,513			-1,403,303
Total segment asset - net book value	2,801,282			2,835,467
Reconciling items:
Cash and cash equivalents	826	853		502	1,897
Restricted cash	14,441			13,811
Deferred financing costs, net	4,118			4,475
Other assets	22,714			24,029
Total consolidated assets	2,843,381			2,878,284
Reportable Segment (Textual) [Abstract]
Related Party Transaction, Management Fee Percentage	2.75%
Number of reportable segments	2
Number of Tenants or related group of tenants that contributed 10% or more of company total revenue	0	0
United Dominion Reality L.P. [Member] \| Same-Store [Member]
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	7,900	3,900
United Dominion Reality L.P. [Member] \| Same Store Communities Western Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	47,815		44,238
Reportable apartment home segment NOI	35,277		32,089
Reportable apartment home segment assets:
Total segment assets	1,690,647			1,686,127
United Dominion Reality L.P. [Member] \| Same Store Communities Mid-Atlantic Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	17,249		17,246
Reportable apartment home segment NOI	11,466		11,565
Reportable apartment home segment assets:
Total segment assets	714,425			713,093
United Dominion Reality L.P. [Member] \| Same Store Communities Northeast Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	15,072		14,268
Reportable apartment home segment NOI	11,572		10,638
Reportable apartment home segment assets:
Total segment assets	778,378			777,376
United Dominion Reality L.P. [Member] \| Same Store Communities Southeastern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	11,679		11,131
Reportable apartment home segment NOI	7,710		7,457
Reportable apartment home segment assets:
Total segment assets	334,282			333,428
United Dominion Reality L.P. [Member] \| Same Store Communities Southwestern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	6,737		6,553
Reportable apartment home segment NOI	4,213		4,217
Reportable apartment home segment assets:
Total segment assets	229,627			228,996
United Dominion Reality L.P. [Member] \| Non-Mature communities/Other [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	11,543		8,934
Reportable apartment home segment NOI	7,877		6,451
Reportable apartment home segment assets:
Total segment assets	501,436			499,750
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	472	256
United Dominion Reality L.P. [Member] \| Total Communities [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	110,095		102,370
Taxable REIT Subsidiaries [Member] \| United Dominion Reality L.P. [Member]
Reportable Segment (Textual) [Abstract]
Related Party Transaction, Management Fee Percentage	2.75%
Segment Reconciling Items [Member] \| United Dominion Reality L.P. [Member]
Reconciling items:
Real estate depreciation and amortization	$44,478		$44,271

Reportable_Segments_UNITED_DOM2

Reportable Segments (UNITED DOMINION REALTY, L.P.) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
	Segments	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Same Store Communities	36,063
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	$219,753	$198,039
Reportable apartment home segment NOI	-143,575	-132,124
Reconciling items:
Property management	-5,694	-5,346
Other operating expenses	-1,766	-1,935
Real estate depreciation and amortization	88,777	88,533
General and administrative	-12,152	-11,994
Casualty-related (recoveries)/charges, net	996	500
Casualty (Recoveries)/Charges	-996	-500
Interest expense	28,800	-32,884
Gains/(loss) on sales of real estate owned	0	24,294
Net (income)/loss attributable to noncontrolling interests	-7	-4
Net income/(loss) attributable to OP unitholders	73,822	18,361
Reportable apartment home segment assets:
Total segment assets	8,453,648			8,383,259
Accumulated depreciation	-2,522,100			-2,434,772
Total segment asset - net book value	5,931,548			5,948,487
Reconciling items:
Cash and cash equivalents	6,274	15,891		15,224	30,249
Restricted cash	23,266			22,340
Deferred financing costs, net	21,676			22,686
Other assets	96,713			105,202
Total consolidated assets	6,858,511			6,846,534
Reportable Segment (Textual) [Abstract]
Number of reportable segments	2
Condition for Community considered to have stabilized occupancy	0.9
Time to maintain percent occupancy to be considered a community	3 months
Number of Tenants or related group of tenants that contributed 10% or more of company total revenue	0	0
Same Store Communities Western Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	67,857	63,267
Reportable apartment home segment NOI	-50,228	-45,408
Reportable apartment home segment assets:
Total segment assets	2,626,770			2,620,242
Same Store Communities Mid-Atlantic Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	42,795	42,049
Reportable apartment home segment NOI	-29,288	-28,835
Reportable apartment home segment assets:
Total segment assets	1,536,389			1,533,993
Same Store Communities Northeast Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	20,892	19,803
Reportable apartment home segment NOI	-15,566	-14,546
Reportable apartment home segment assets:
Total segment assets	1,078,431			1,076,656
Same Store Communities Southeastern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	27,829	26,497
Reportable apartment home segment NOI	-18,547	-17,872
Reportable apartment home segment assets:
Total segment assets	788,668			786,438
Same Store Communities Southwestern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	14,107	13,467
Reportable apartment home segment NOI	-8,536	-8,358
Reportable apartment home segment assets:
Total segment assets	441,888			440,721
Non-Mature communities/Other [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	33,567	29,317
Reportable apartment home segment NOI	-21,410	-17,105
Reportable apartment home segment assets:
Total segment assets	1,981,502			1,925,209
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	2,500	2,100
Total Communities [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	207,047	194,400
United Dominion Reality L.P. [Member]
Segment Reporting Information [Line Items]
Same Store Communities	19,209
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment NOI	-78,115		-72,417
Reconciling items:
Property management	-3,027		-2,815
Other operating expenses	-1,490		-1,436
Real estate depreciation and amortization	44,478	44,271
General and administrative	-5,639		-6,970
Casualty (Recoveries)/Charges	-593	-500	500
Interest expense	-10,771		-10,014
Gains/(loss) on sales of real estate owned	24,623	24,402
Net (income)/loss attributable to noncontrolling interests	-394		-280
Net income/(loss) attributable to OP unitholders	36,346	30,533	30,533
Reportable apartment home segment assets:
Total segment assets	4,248,795			4,238,770
Accumulated depreciation	-1,447,513			-1,403,303
Total segment asset - net book value	2,801,282			2,835,467
Reconciling items:
Cash and cash equivalents	826	853		502	1,897
Restricted cash	14,441			13,811
Deferred financing costs, net	4,118			4,475
Other assets	22,714			24,029
Total consolidated assets	2,843,381			2,878,284
Reportable Segment (Textual) [Abstract]
Number of reportable segments	2
Number of Tenants or related group of tenants that contributed 10% or more of company total revenue	0	0
Related Party Transaction, Management Fee Percentage	2.75%
United Dominion Reality L.P. [Member] \| Same-Store [Member]
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	7,900	3,900
United Dominion Reality L.P. [Member] \| Same Store Communities Western Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	47,815		44,238
Reportable apartment home segment NOI	-35,277		-32,089
Reportable apartment home segment assets:
Total segment assets	1,690,647			1,686,127
United Dominion Reality L.P. [Member] \| Same Store Communities Mid-Atlantic Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	17,249		17,246
Reportable apartment home segment NOI	-11,466		-11,565
Reportable apartment home segment assets:
Total segment assets	714,425			713,093
United Dominion Reality L.P. [Member] \| Same Store Communities Northeast Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	15,072		14,268
Reportable apartment home segment NOI	-11,572		-10,638
Reportable apartment home segment assets:
Total segment assets	778,378			777,376
United Dominion Reality L.P. [Member] \| Same Store Communities Southeastern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	11,679		11,131
Reportable apartment home segment NOI	-7,710		-7,457
Reportable apartment home segment assets:
Total segment assets	334,282			333,428
United Dominion Reality L.P. [Member] \| Same Store Communities Southwestern Region [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	6,737		6,553
Reportable apartment home segment NOI	-4,213		-4,217
Reportable apartment home segment assets:
Total segment assets	229,627			228,996
United Dominion Reality L.P. [Member] \| Non-Mature communities/Other [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	11,543		8,934
Reportable apartment home segment NOI	-7,877		-6,451
Reportable apartment home segment assets:
Total segment assets	501,436			499,750
Reportable Segment (Textual) [Abstract]
SEC Schedule III, Real Estate, Improvements	472	256
United Dominion Reality L.P. [Member] \| Total Communities [Member]
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Reportable apartment home segment rental income	110,095		102,370
Segment Reconciling Items [Member] \| United Dominion Reality L.P. [Member]
Reconciling items:
Real estate depreciation and amortization	$44,478		$44,271