Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)

v3.7.0.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)
$ in Thousands
Jun. 30, 2017
USD ($)
partnership
property
Dec. 31, 2016
USD ($)
partnership
property
Variable Interest Entity [Line Items]    
Number of self storage properties owned | property 394  
Net book value of real estate owned $ 1,815,330 $ 1,733,533
Carrying value of fixed rate mortgages 964,932 $ 873,194
Number of properties held for sale | property   2
Mortgages [Member] | Fixed Rate Mortgages [Member]    
Variable Interest Entity [Line Items]    
Carrying value of fixed rate mortgages $ 188,932 $ 201,694
Variable Interest Entity, Primary Beneficiary [Member]    
Variable Interest Entity [Line Items]    
Number of partnerships considered to be VIEs | partnership 21 21
Number of self storage properties owned | property 34 34
Net book value of real estate owned $ 252,900 $ 256,800
Variable Interest Entity, Primary Beneficiary [Member] | Mortgages [Member] | Fixed Rate Mortgages [Member]    
Variable Interest Entity [Line Items]    
Carrying value of fixed rate mortgages $ 40,500 $ 41,400