NONCONTROLLING INTEREST REPRESENTED BY PREFERRED OPERATING PARTNERSHIP UNITS (Details) (USD $) In Thousands, except Share data, unless otherwise specified			1 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2007 Preferred Operating Partnership	Jun. 30, 2011 Preferred Operating Partnership	Jun. 25, 2007 Preferred Operating Partnership
Noncontrolling interest represented by preferred operating partnership units
Number of self-storage facilities (properties) acquired			10
Preferred OP units (in units)			989,980
Loan to holders of preferred OP units	$ 100,000	$ 100,000			$ 100,000
Note receivable interest rate (as a percent)			4.85%
Maximum number of preferred OP units converted prior to the maturity date of the loan (in units)			114,500
Fixed priority return on preferred OP units, amount				115,000
Fixed priority return on preferred OP units, stated return rate (as a percent)				5.00%
Fixed priority return on preferred OP units, liquidation value				$ 115,000