JOINT VENTURES AND PARTNERSHIPS - Commitments (Details) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Jan. 31, 2020 USD ($) home	Jan. 31, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Joint Ventures
Real estate owned			$ 12,861,020		$ 12,861,020		$ 12,602,101
First installment of payable incurred in partial consideration for acquisition of ownership interest in joint venture			2,680		2,680
Second installment of payable incurred in partial consideration for acquisition of ownership interest in joint venture			24,874		24,874
Investment in unconsolidated entities			641,858		$ 641,858		585,490
Condition for Community considered to have stabilized occupancy					90%
Time to maintain percent occupancy to be considered a community					3 months
Investment in unconsolidated joint ventures					$ 66,893	$ 72,079
Long-term Debt			4,917,646		4,917,646		4,707,524
Liabilities			5,457,950		5,457,950		5,228,493
Deferred fees from the sale of properties			8,600		8,600		$ 9,000
Gain/(loss) on sales of real estate owned					61,303	5,282
Joint venture management and other fees			$ 1,199	$ 6,386	$ 3,861	$ 11,982
Type of revenue			udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Preferred Equity Investment Hillsboro Oregon
Joint Ventures
UDR's Ownership Interest	100.00%						49.00%
repayment of construction loan		$ 35,600
Payment to acquire real estate	$ 21,600
Number of apartment homes | home	276
13th and Market Properties LLC
Joint Ventures
Investment in unconsolidated entities			$ (4,500)		$ (4,500)