Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)

v3.8.0.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)
$ in Thousands
Sep. 30, 2017
USD ($)
partnership
property
Dec. 31, 2016
USD ($)
partnership
property
Variable Interest Entity [Line Items]    
Number of self storage properties owned | property 413  
Net book value of real estate owned $ 1,922,062 $ 1,733,533
Carrying value of fixed rate mortgages 1,068,678 $ 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 $ 272,678 $ 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 $ 249,900 $ 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 $ 140,800 $ 41,400