SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Operating Partnership, Purchase Allocation, Depreciation and Amortization (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) facility	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Operating Partnership Ownership
Increase (decrease) to OP units owned by third parties and a corresponding decrease to capital	$ 5,918	$ 299	$ 3,965
Purchase Price Allocation
Amount of purchase price allocated to above- or below-market lease intangibles	0
Depreciation and Amortization
Impairment losses	$ 0	0	0
Number of stores classified as held-for-sale | facility	0
Minimum
Depreciation and Amortization
Useful lives of self-storage facilities and improvements	5 years
Maximum
Depreciation and Amortization
Useful lives of self-storage facilities and improvements	39 years
Cubesmart, L P and Subsidiaries
Operating Partnership Ownership
Increase (decrease) to OP units owned by third parties and a corresponding decrease to capital	$ 5,918	$ 299	$ 3,965