Quarterly report pursuant to Section 13 or 15(d)

Investment in Storage Facilities - Schedule of Acquired Facilities and Purchase Price of Facilities (Detail)

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Investment in Storage Facilities - Schedule of Acquired Facilities and Purchase Price of Facilities (Detail)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2016
USD ($)
Facility
Property
Mar. 31, 2015
USD ($)
Dec. 31, 2015
USD ($)
Investment Holdings [Line Items]      
Number of Properties | Facility 25    
Cash Paid $ 326,000    
Closing Costs Expensed $ 2,384 $ 582  
Acquisitions 2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 25    
Purchase Price $ 331,801    
Cash Paid 326,048    
Consideration paid Value of Operating Partnership Units Issued 4,472    
Net Other Liabilities (Assets) Assumed 1,281    
Land 114,738    
Acquisition Date Building, Equipment, and Improvements 212,670    
Fair Value In-Place Customer Leases 4,393    
Closing Costs Expensed $ 2,384   $ 345
Florida [Member] | Date Of Acquisition, 1/6/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 4    
Date of Acquisition Jan. 06, 2016    
Purchase Price $ 20,350    
Cash Paid 20,246    
Net Other Liabilities (Assets) Assumed 104    
Land 6,646    
Acquisition Date Building, Equipment, and Improvements 13,339    
Fair Value In-Place Customer Leases 365    
Closing Costs Expensed $ 366    
Florida [Member] | Date Of Acquisition, 2/12/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 1    
Date of Acquisition Feb. 12, 2016    
Purchase Price $ 11,274    
Cash Paid 11,270    
Net Other Liabilities (Assets) Assumed 4    
Land 2,294    
Acquisition Date Building, Equipment, and Improvements $ 8,980    
California [Member] | Date Of Acquisition, 1/21/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 4    
Date of Acquisition Jan. 21, 2016    
Purchase Price $ 78,750    
Cash Paid 78,562    
Net Other Liabilities (Assets) Assumed 188    
Land 27,876    
Acquisition Date Building, Equipment, and Improvements 49,860    
Fair Value In-Place Customer Leases 1,014    
Closing Costs Expensed $ 327    
California [Member] | Date Of Acquisition, 3/16/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 3    
Date of Acquisition Mar. 16, 2016    
Purchase Price $ 68,832    
Cash Paid 63,965    
Consideration paid Value of Operating Partnership Units Issued 4,472    
Net Other Liabilities (Assets) Assumed 395    
Land 22,647    
Acquisition Date Building, Equipment, and Improvements 45,371    
Fair Value In-Place Customer Leases 814    
Closing Costs Expensed $ 260    
California [Member] | Date Of Acquisition, 3/17/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 1    
Date of Acquisition Mar. 17, 2016    
Purchase Price $ 17,320    
Cash Paid 17,278    
Net Other Liabilities (Assets) Assumed 42    
Land 6,728    
Acquisition Date Building, Equipment, and Improvements 10,339    
Fair Value In-Place Customer Leases 253    
Closing Costs Expensed $ 115    
New Hampshire [Member] | Date Of Acquisition, 1/21/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 5    
Date of Acquisition Jan. 21, 2016    
Purchase Price $ 54,225    
Cash Paid 53,941    
Net Other Liabilities (Assets) Assumed 284    
Land 12,902    
Acquisition Date Building, Equipment, and Improvements 40,428    
Fair Value In-Place Customer Leases 895    
Closing Costs Expensed $ 569    
Massachusetts [Member] | Date Of Acquisition, 1/21/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 1    
Date of Acquisition Jan. 21, 2016    
Purchase Price $ 11,375    
Cash Paid 11,350    
Net Other Liabilities (Assets) Assumed 25    
Land 4,874    
Acquisition Date Building, Equipment, and Improvements 6,335    
Fair Value In-Place Customer Leases 166    
Closing Costs Expensed $ 64    
Texas [Member] | Date Of Acquisition, 1/21/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 3    
Date of Acquisition Jan. 21, 2016    
Purchase Price $ 42,050    
Cash Paid 41,894    
Net Other Liabilities (Assets) Assumed 156    
Land 23,487    
Acquisition Date Building, Equipment, and Improvements 18,000    
Fair Value In-Place Customer Leases 563    
Closing Costs Expensed $ 247    
Arizona [Member] | Date Of Acquisition, 2/1/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 1    
Date of Acquisition Feb. 01, 2016    
Purchase Price $ 9,275    
Cash Paid 9,261    
Net Other Liabilities (Assets) Assumed 14    
Land 988    
Acquisition Date Building, Equipment, and Improvements 8,224    
Fair Value In-Place Customer Leases 63    
Closing Costs Expensed $ 119    
Pennsylvania [Member] | Date Of Acquisition, 2/17/2016[Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 1    
Date of Acquisition Feb. 17, 2016    
Purchase Price $ 5,750    
Cash Paid 5,732    
Net Other Liabilities (Assets) Assumed 18    
Land 1,768    
Acquisition Date Building, Equipment, and Improvements 3,879    
Fair Value In-Place Customer Leases 103    
Closing Costs Expensed $ 147    
Colorado [Member] | Date Of Acquisition, 2/29/2016 [Member]      
Investment Holdings [Line Items]      
Number of Properties | Property 1    
Date of Acquisition Feb. 29, 2016    
Purchase Price $ 12,600    
Cash Paid 12,549    
Net Other Liabilities (Assets) Assumed 51    
Land 4,528    
Acquisition Date Building, Equipment, and Improvements 7,915    
Fair Value In-Place Customer Leases 157    
Closing Costs Expensed $ 170