NONCONTROLLING INTERESTS - Operating Partnership Ownership (Details) - USD ($) $ in Thousands			3 Months Ended				6 Months Ended	12 Months Ended
	Dec. 16, 2019	Jan. 31, 2018	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Dec. 31, 2019
Operating Partnership Ownership
OP Units outstanding which are not owned by the general partner (as a percent)			1.00%				1.00%	1.00%
Elimination of noncontrolling interest in subsidiaries due to acquisition					$ 27,618	$ 10,000
Adjustment for noncontrolling interest in the Operating Partnership			$ (615)	$ 7,976	(2,713)	(6,681)	$ 7,400	$ 5,900
California
Operating Partnership Ownership
OP units issued (in shares)	106,738
Issuance of OP Shares	$ 3,600
Total consideration	18,500
Cash paid for acquisition	$ 14,900
Texas
Operating Partnership Ownership
OP units issued (in shares)		168,011
Issuance of OP Shares		$ 4,800
Total consideration		12,200
Cash paid for acquisition		200
Amount of mortgage loan commitment		$ 7,200
Cubesmart, L P and Subsidiaries
Operating Partnership Ownership
OP units outstanding (in shares)			1,872,308				1,872,308	1,972,308
Number of trading days used to determine average of the closing prices of the shares							10 days
Elimination of noncontrolling interest in subsidiaries due to acquisition					27,618	10,000
Adjustment for noncontrolling interest in the Operating Partnership			$ (615)	$ 7,976	$ (2,713)	$ (6,681)