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
Mar. 31, 2017
USD ($)
partnership
property
Dec. 31, 2016
USD ($)
property
Variable Interest Entity [Line Items]    
Number of self storage properties owned | property 386  
Net book value of real estate owned $ 1,762,314 $ 1,733,533
Carrying value of fixed rate mortgages 889,437 $ 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 $ 191,937 $ 201,694
Variable Interest Entity, Primary Beneficiary [Member]    
Variable Interest Entity [Line Items]    
Number of partnerships considered to be VIEs | partnership 21  
Number of self storage properties owned | property 34  
Net book value of real estate owned $ 254,800 256,800
Variable Interest Entity, Primary Beneficiary [Member] | Mortgages [Member] | Fixed Rate Mortgages [Member]    
Variable Interest Entity [Line Items]    
Carrying value of fixed rate mortgages $ 41,000 $ 41,400