Annual report pursuant to Section 13 and 15(d)

Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Parenthetical) (Detail)

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Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Parenthetical) (Detail)
$ in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
Facility
4.98% Mortgage Note Due January 1, 2021 [Member]  
Debt Instrument [Line Items]  
Interest rate 4.98%
Mortgage note due date Jan. 01, 2021
Self-storage facilities | Facility 1
Aggregate net book value of property pledged for mortgage note | $ $ 9.5
Effective interest rate 5.22%
4.065% Mortgage Note Due April 1, 2023 [Member]  
Debt Instrument [Line Items]  
Interest rate 4.065%
Mortgage note due date Apr. 01, 2023
Self-storage facilities | Facility 1
Aggregate net book value of property pledged for mortgage note | $ $ 7.4
Effective interest rate 4.30%
5.26% Mortgage Note Due November 1, 2023 [Member]  
Debt Instrument [Line Items]  
Interest rate 5.26%
Mortgage note due date Nov. 01, 2023
Self-storage facilities | Facility 1
Aggregate net book value of property pledged for mortgage note | $ $ 7.9
Effective interest rate 5.57%
5.99% Mortgage Note Due May 1, 2026 [Member]  
Debt Instrument [Line Items]  
Interest rate 5.99%
Mortgage note due date May 01, 2026
Self-storage facilities | Facility 1
Aggregate net book value of property pledged for mortgage note | $ $ 6.5
Effective interest rate 6.25%