COMMITMENTS AND CONTINGENCIES - Real Estate Commitments (Details) $ in Thousands	1 Months Ended
	Nov. 30, 2019 USD ($) home	Dec. 31, 2019 USD ($) item community
Commitments
Number of communities owned (in communities) | community		148
Cost Incurred to Date		$ 172,964
UDR's Remaining Commitment		$ 245,700
Wholly owned - under development
Commitments
Number of communities owned (in communities) | item		3
Cost Incurred to Date		$ 69,754
UDR's Remaining Commitment		$ 208,723
Wholly owned - redevelopment
Commitments
Number of communities owned (in communities) | item		2
Cost Incurred to Date		$ 15,744
UDR's Remaining Commitment		$ 19,756
Preferred Equity Investments
Commitments
Number of communities owned (in communities) | item		2
Cost Incurred to Date		$ 73,868
UDR's Remaining Commitment		9,121
Other investments
Commitments
Cost Incurred to Date		13,598
UDR's Remaining Commitment		8,100
Bellevue, WA 259 Home Community
Commitments
Aggregate commitment on note receivable		115,000
Number of apartment homes | home	259
Payment to acquire real estate	$ 170,000
King of Prussia
Commitments
Contractual purchase price commitment		14,800
Deposit on purchase		800
Deposit On Purchase Commitment		$ 800