Debt - Additional Information (Detail)
3 Months Ended 7 Months Ended 9 Months Ended
Jun. 01, 2017
USD ($)
Apr. 11, 2017
USD ($)
Property
Entity
Mar. 08, 2017
USD ($)
Property
Mar. 07, 2017
Dec. 29, 2016
USD ($)
Jul. 28, 2016
USD ($)
Entity
Mar. 25, 2016
USD ($)
Property
Dec. 31, 2016
USD ($)
Sep. 30, 2016
USD ($)
Dec. 28, 2016
Sep. 30, 2017
USD ($)
Property
Extension
Sep. 30, 2016
USD ($)
May 01, 2017
USD ($)
Mar. 31, 2017
CAD
Feb. 01, 2017
CAD
Dec. 30, 2016
USD ($)
Jun. 01, 2016
USD ($)
Feb. 18, 2016
USD ($)
Dec. 22, 2015
USD ($)
Debt Instrument [Line Items]                                      
Weighted average interest rate on debt                     4.26%                
Guarantees provided in connection with loans                     $ 43,700,000                
Number of properties removed from encumbrance | Property     5                                
Principal payments on debt                     127,671,050 $ 125,154,150              
Loans outstanding                     $ 401,414,700                
Notional amount for interest rate cap | CAD                           CAD 101,000,000 CAD 58,500,000        
Number of special purpose entities | Entity   5                                  
27 Property Portfolio                                      
Debt Instrument [Line Items]                                      
Number of self storage facilities | Property             22                        
27 Property Portfolio | Florida                                      
Debt Instrument [Line Items]                                      
Number of self storage facilities | Property             10                        
27 Property Portfolio | North Carolina                                      
Debt Instrument [Line Items]                                      
Number of self storage facilities | Property             11                        
27 Property Portfolio | Maryland                                      
Debt Instrument [Line Items]                                      
Number of self storage facilities | Property             1                        
First Phase | 27 Property Portfolio                                      
Debt Instrument [Line Items]                                      
Purchase price of Property             $ 275,000,000                        
Operating Partnership                                      
Debt Instrument [Line Items]                                      
Notional amount for interest rate cap                         $ 90,000,000     $ 100,000,000      
Effective interest rate cap on derivative instrument                         1.25%            
LIBOR | Operating Partnership                                      
Debt Instrument [Line Items]                                      
Effective interest rate cap on derivative instrument                               1.50%      
Amended KeyBank Property Loan                                      
Debt Instrument [Line Items]                                      
Number of properties removed from encumbrance | Property   5                                  
Maturity date of loan     Mar. 31, 2017 May 01, 2017                              
KeyBank Property Loan                                      
Debt Instrument [Line Items]                                      
Number of properties encumbered | Property                     5                
KeyBank Florida CMBS Loan                                      
Debt Instrument [Line Items]                                      
Outstanding principal amount   $ 52,000,000                                  
Maturity date of loan   May 01, 2027                                  
Debt instrument initial term   10 years                                  
Debt Instrument, Periodic Payment                     Monthly payments due are interest-only for the first five years and payments reflecting a 30-year amortization schedule begin thereafter.                
Debt Instrument, Interest Rate   4.65%                                  
KeyBank CMBS Loan                                      
Debt Instrument [Line Items]                                      
Number of special purpose entities | Entity           29                          
$11M KeyBank Subordinate Loan                                      
Debt Instrument [Line Items]                                      
Loans outstanding [1]               $ 0     $ 11,000,000                
Maturity date of loan [1]                     Jun. 01, 2020                
Debt Instrument, Interest Rate [1]                     4.99%                
Number of properties encumbered | Property                     34                
Loans Payable [Member]                                      
Debt Instrument [Line Items]                                      
Outstanding principal amount         $ 92,800,000                            
Loans Payable [Member] | Amended KeyBank Property Loan                                      
Debt Instrument [Line Items]                                      
Principal payments on debt     $ 46,000,000                                
Maturity date of loan         Mar. 31, 2017         Dec. 31, 2016                  
Loans Payable [Member] | Amended KeyBank Subordinate Loan                                      
Debt Instrument [Line Items]                                      
Principal payments on debt               20,000,000 $ 20,000,000                    
Loans outstanding     10,000,000                                
Outstanding principal amount     $ 10,000,000                                
Maturity date of loan         Mar. 31, 2017         Dec. 31, 2016                  
Loans Payable [Member] | KeyBank Property Loan                                      
Debt Instrument [Line Items]                                      
Outstanding principal amount                                 $ 105,000,000    
Maturity date of loan                     Dec. 31, 2016                
Loans Payable [Member] | KeyBank Subordinate Loan [Member]                                      
Debt Instrument [Line Items]                                      
Outstanding principal amount                                 $ 30,000,000    
Maturity date of loan                     Dec. 31, 2016                
Fixed Rate Secured Debt | KeyBank Florida CMBS Loan                                      
Debt Instrument [Line Items]                                      
Loans outstanding [2]               0     $ 52,000,000                
Maturity date of loan [2]                     May 01, 2027                
Debt Instrument, Interest Rate [2]                     4.65%                
Number of properties encumbered | Property                     5                
Fixed Rate Secured Debt | KeyBank CMBS Loan                                      
Debt Instrument [Line Items]                                      
Loans outstanding [3]               95,000,000     $ 95,000,000                
Outstanding principal amount           $ 95,000,000                          
Maturity date of loan           Aug. 01, 2026         Aug. 01, 2026 [3]                
Debt instrument initial term           10 years                          
Debt Instrument, Interest Rate           3.89%         3.89% [3]                
Number of properties encumbered | Property                     29                
Fixed Rate Secured Debt | $11M KeyBank Subordinate Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, interest rate description                     An ABR Borrowing bears interest at the lesser of (x) the Alternate Base Rate (as defined in the $11M Subordinate Loan Agreement) plus the Applicable Rate, or (y) the Maximum Rate (as defined in the $11M Subordinate Loan Agreement). A Eurodollar Borrowing bears interest at the lesser of (a) the Adjusted LIBO Rate (as defined in the $11M Subordinate Loan Agreement) for the Interest Period in effect plus the Applicable Rate, or (b) the Maximum Rate (as defined in the $11M Subordinate Loan Agreement). The Applicable Rate means 375 basis points for any Eurodollar Borrowing and 275 basis points for any ABR Borrowing.                
Outstanding principal amount $ 11,000,000                                    
Number of properties encumbered | Property                     34                
Fixed Rate Secured Debt | $11M KeyBank Subordinate Loan | ABR Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, applicable interest rate 2.75%                                    
Fixed Rate Secured Debt | $11M KeyBank Subordinate Loan | Eurodollar Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, applicable interest rate 3.75%                                    
Promissory Notes Payable One | KeyBank CMBS Loan                                      
Debt Instrument [Line Items]                                      
Outstanding principal amount           $ 70,000,000                          
Debt Instrument, Periodic Payment                     Monthly payments due under the Promissory Notes are interest-only for the first five years and payments reflecting a 30-year amortization schedule begin thereafter.                
Promissory Notes Payable Two | KeyBank CMBS Loan                                      
Debt Instrument [Line Items]                                      
Outstanding principal amount           $ 25,000,000                          
Debt Instrument, Periodic Payment                     Monthly payments due under the Promissory Notes are interest-only for the first five years and payments reflecting a 30-year amortization schedule begin thereafter.                
KeyBank Credit Facility                                      
Debt Instrument [Line Items]                                      
Maximum borrowings under credit facility                                     $ 71,300,000
Amended KeyBank Credit Facility                                      
Debt Instrument [Line Items]                                      
Maximum borrowings under credit facility                                   $ 145,000,000 105,000,000
Potential maximum borrowings under credit facility                                     500,000,000
Increment in borrowing capacity                                     $ 10,000,000
Additional borrowing capacity                                   $ 40,000,000  
Number of properties removed from encumbrance | Property     5                                
Outstanding balance on credit facility     $ 56,000,000                                
Loans outstanding [4]               $ 12,300,000     $ 89,382,500                
Line of credit facility, initial term                     3 years                
Line of credit facility, maturity date                     Dec. 22, 2018                
Line of credit facility, term of extension options                     1 year                
Line of credit facility, number of extension options | Extension                     2                
Line of credit facility, description                     The Amended KeyBank Credit Facility is a revolving loan with an initial term of three years, maturing on December 22, 2018, with two one-year extension options subject to certain conditions outlined further in the credit agreement for the Amended KeyBank Credit Facility (the “Amended Credit Agreement”). Payments due pursuant to the Amended KeyBank Credit Facility are interest-only for the first 36 months and a 30-year amortization schedule thereafter.                
Line of credit facility amortization schedule                     30 years                
Line of credit facility interest-only period                     36 months                
Line of credit facility, interest rate description                     The Eurodollar Loans bear interest at the lesser of (a) the Adjusted LIBO Rate (as defined in the Amended Credit Agreement) for the Interest Period in effect plus the Applicable Rate, or (b) the Maximum Rate (as defined in the Amended Credit Agreement). The Applicable Rate corresponds to our total leverage, as specified in the Amended Credit Agreement. For any ABR Loans, the Applicable Rate is 125 basis points if our total leverage is less than 50%, and 150 basis points if our leverage is greater than 50%. For any Eurodollar Loan, the Applicable Rate is 225 basis points if our total leverage is less than 50% and 250 basis points if our total leverage is greater than 50%.                
Percent of collateral properties used for aggregate borrowing capacity                     60.00%                
Minimum debt service coverage ratio                     1.35%                
Total leverage ratio                     60.00%                
Percentage of net proceeds of equity received                     80.00%                
Minimum interest service coverage ratio                     1.85%                
Minimum fixed charge ratio                     1.60%                
Threshold percentage for ratio of variable rate indebtedness to total indebtedness.                     30.00%                
Percentage of required loan to value ratio                     60.00%                
Maturity date of loan [4]                     Dec. 22, 2018                
Number of properties encumbered | Property                     21                
Amended KeyBank Credit Facility | Fixed Rate Secured Debt | Loans Payable [Member]                                      
Debt Instrument [Line Items]                                      
Outstanding balance on credit facility                     $ 89,000,000                
Amended KeyBank Credit Facility | Loans with Total Leverage Less Than 50% | ABR Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, applicable interest rate                     1.25%                
Amended KeyBank Credit Facility | Loans with Total Leverage Less Than 50% | Eurodollar Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, applicable interest rate                     2.25%                
Amended KeyBank Credit Facility | Loans with Total Leverage Greater Than 50% | ABR Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, applicable interest rate                     1.50%                
Amended KeyBank Credit Facility | Loans with Total Leverage Greater Than 50% | Eurodollar Loan                                      
Debt Instrument [Line Items]                                      
Line of credit facility, applicable interest rate                     2.50%                
[1] This loan encumbers the equity interest in the entities that own the 34 properties (the 29 properties encumbered by the KeyBank CMBS Loan and the five properties encumbered by the KeyBank Florida CMBS Loan), and is subordinate to the existing KeyBank CMBS Loan and KeyBank Florida CMBS Loan.
[2] This loan encumbers five properties (Pompano Beach, Lake Worth, Jupiter, Royal Palm Beach, and Delray). The separate assets of these encumbered properties are not available to pay our other debts.
[3] This loan encumbers 29 properties (Whittier, La Verne, Santa Ana, Upland, La Habra, Monterey Park, Huntington Beach, Chico, Lancaster I, Riverside, Fairfield, Lompoc, Santa Rosa, Federal Heights, Aurora, Littleton, Bloomingdale, Crestwood, Forestville, Warren I, Sterling Heights, Troy, Warren II, Beverly, Everett, Foley, Tampa, Boynton Beach, and Lancaster II). The separate assets of these encumbered properties are not available to pay our other debts.
[4] As of September 30, 2017, this facility encumbers 21 properties (Xenia, Sidney, Troy, Greenville, Washington Court House, Richmond, Connersville, Vallejo, Port St. Lucie I, Sacramento, Sonoma, Las Vegas I, Las Vegas II, Las Vegas III, Baltimore, Aurora II, Plantation, Wellington, Naples, Port St. Lucie II, and Doral).