Annual report pursuant to Section 13 and 15(d)

Investment in Joint Ventures - Summary of Unconsolidated Joint Ventures' Financial Statements (Detail)

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Investment in Joint Ventures - Summary of Unconsolidated Joint Ventures' Financial Statements (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]        
Investment in storage facilities, net $ 3,697,096 $ 3,707,604    
Other assets 4,863 29,554    
Total Assets 3,876,774 3,857,984    
Mortgages payable 12,674 13,027    
Total Liabilities 1,829,078 1,751,399    
Unaffiliated partners’ equity 0 0    
Company equity 2,028,323 2,088,494 $ 1,202,315 $ 975,869
Total Equity 2,028,323 2,088,494    
Depreciation and amortization of customer list (127,485) (117,081) (58,506)  
Amortization of financing fees (4,289) (9,688) (1,184)  
Interest expense (74,362) $ (47,175) $ (37,124)  
Unconsolidated Joint Ventures [Member]        
Schedule of Equity Method Investments [Line Items]        
Investment in storage facilities, net 1,075,101      
Investment in office building, net 4,810      
Other assets 16,622      
Total Assets 1,096,533      
Due to the Company 1,397      
Mortgages payable 459,028      
Other liabilities 10,721      
Total Liabilities 471,146      
Unaffiliated partners’ equity 492,332      
Company equity 133,055      
Total Equity 625,387      
Total Liabilities and Partners’ Equity 1,096,533      
Total revenues 96,301      
Property operating expenses (31,008)      
Administrative, management and call center fees (7,668)      
Depreciation and amortization of customer list (21,165)      
Amortization of financing fees (810)      
Income tax expense (252)      
Interest expense (14,571)      
Net income $ 20,827