Quarterly report pursuant to Section 13 or 15(d)

Investment in Storage Facilities and Intangible Assets - Additional Information (Detail)

v3.10.0.1
Investment in Storage Facilities and Intangible Assets - Additional Information (Detail)
3 Months Ended 9 Months Ended
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
$ / shares
Sep. 30, 2017
USD ($)
$ / shares
Sep. 30, 2018
USD ($)
Property
$ / shares
Sep. 30, 2017
USD ($)
$ / shares
Investment Holdings [Line Items]          
Number of storage facilities acquired | Property       2  
Net other liabilities assumed       $ 78,000  
Amortization period for in-place customer leases on a straight-line basis       12 months  
Amortization expense related to in-place customer leases   $ 9,000 $ 100,000 $ 9,000 $ 24,800,000
Amortization expense expected for 2018   100,000   100,000  
Amortization expense expected for 2019   200,000   200,000  
Net proceeds from the sale of real estate       10,576,000 1,994,000
Gain on sale of non-strategic property   718,000   718,000  
Increase in depreciation expense due to facility replacement   $ 2,400,000 $ 2,000,000 $ 2,800,000 $ 3,600,000
Accelerated depreciation reduced basic and diluted earnings per share | $ / shares   $ 0.04 $ 0.04 $ 0.05 $ 0.07
Scenario, Forecast [Member]          
Investment Holdings [Line Items]          
Increase in depreciation expense due to facility replacement $ 500,000        
Property Dispositions [Member]          
Investment Holdings [Line Items]          
Number Of Properties Sold | Property       1  
Net proceeds from the sale of real estate       $ 9,600,000  
Gain on sale of non-strategic property       $ 900,000