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
3 Months Ended 12 Months Ended
Dec. 31, 2021
Sep. 30, 2021
Jun. 30, 2021
Mar. 31, 2021
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]                        
Investment in storage facilities, net $ 6,082,807       $ 4,457,145       $ 6,082,807 $ 4,457,145    
Other assets 44,387       31,907       44,387 31,907    
Total Assets 6,556,597       4,727,848       6,556,597 4,727,848    
Mortgages payable 37,030       37,777       37,030 37,777    
Total Liabilities 2,943,923       2,323,304       2,943,923 2,323,304    
Company equity 3,378,999       2,378,098       3,378,999 2,378,098 $ 2,132,894 $ 2,057,737
Total Liabilities and Shareholders' Equity/ Partners' Capital 6,556,597       4,727,848       6,556,597 4,727,848    
Total Liabilities 2,943,923       2,323,304       2,943,923 2,323,304    
Total revenues 221,159 $ 208,256 $ 187,262 $ 171,887 166,505 $ 156,310 $ 147,013 $ 146,943 788,565 616,771 574,739  
Depreciation and amortization of customer list                 (147,119) (122,925) (107,130)  
Amortization of financing fees                 (4,513) (4,096) (3,900)  
Interest expense                 (86,786) (86,015) (76,430)  
Net income 75,767 $ 71,051 $ 57,765 $ 47,592 $ 41,799 $ 37,288 $ 36,648 $ 36,625 252,175 $ 152,360 $ 260,077  
Unconsolidated Joint Ventures [Member]                        
Schedule of Equity Method Investments [Line Items]                        
Investment in storage facilities, net 1,650,866               1,650,866      
Investment in office building, net 4,172               4,172      
Other assets 29,153               29,153      
Total Assets 1,684,191               1,684,191      
Due to the Company 333               333      
Mortgages payable 872,574               872,574      
Other liabilities 15,432               15,432      
Total Liabilities 888,339               888,339      
Unaffiliated partners’ equity 587,619               587,619      
Company equity 208,233               208,233      
Total Equity 795,852               795,852      
Total Liabilities and Shareholders' Equity/ Partners' Capital 1,684,191               1,684,191      
Total Liabilities $ 888,339               888,339      
Total revenues                 126,426      
Property operating expenses                 (39,180)      
Administrative, management and call center fees                 (9,531)      
Gain on sale of self-storage facilities                 53,391      
Depreciation and amortization of customer list                 (29,914)      
Amortization of financing fees                 (976)      
Income tax expense                 (217)      
Interest expense                 (21,279)      
Net income                 $ 78,720