Annual report pursuant to Section 13 and 15(d)

Real Estate and Intangible Assets - Summary of Properties Acquired (Detail)

v3.8.0.1
Real Estate and Intangible Assets - Summary of Properties Acquired (Detail)
$ in Thousands
 12 Months Ended
Dec. 01, 2017
USD ($)
ft²
Jul. 31, 2017
USD ($)
ft²
property
Jul. 07, 2017
USD ($)
ft²
Jun. 22, 2017
USD ($)
ft²
Dec. 14, 2016
USD ($)
ft²
Sep. 12, 2016
USD ($)
ft²
May 26, 2016
USD ($)
ft²
Dec. 31, 2017
USD ($)
ft²
Dec. 31, 2016
USD ($)
ft²
Jul. 25, 2014
ft²
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²                   81,371
Aggregate Purchase Price               $ 132,157 $ 66,570  
Acquisition Expenses               1,400    
Number of properties in portfolio | property   3                
Derivative asset               504 101  
Accumulated other comprehensive income               $ (35) $ 0  
Series of Property Acquisitions [Member]                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²               871,038 329,620  
Lease Term               10 years 1 month 6 days 10 years 6 months  
Aggregate Purchase Price               $ 132,157 $ 66,570  
Acquisition Expenses               1,356 179  
Aggregate Annualized GAAP Rent               15,507 5,589  
Aggregate Debt Issued or Assumed               $ 54,887 $ 38,800  
Conshohocken, PA                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²       60,016            
Lease Term       8 years 6 months            
Aggregate Purchase Price       $ 15,700            
Aggregate Annualized GAAP Rent       1,700            
Noncash or part noncash acquisition, debt assumed       $ 11,200            
Philadelphia, PA                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²     300,000              
Lease Term     15 years 4 months 24 days              
Aggregate Purchase Price     $ 27,100              
Aggregate Annualized GAAP Rent     2,300              
Aggregate Debt Issued or Assumed     $ 14,900              
Maitland, Florida                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²   306,435                
Lease Term   8 years 7 months 6 days                
Aggregate Purchase Price   $ 51,600                
Aggregate Annualized GAAP Rent   6,800                
Aggregate Debt Issued or Assumed   $ 28,800                
Columbus, OH                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft² 102,559                  
Lease Term 6 years 10 months 24 days                  
Aggregate Purchase Price $ 17,300                  
Aggregate Annualized GAAP Rent $ 1,700                  
Salt Lake City, UT                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft² 102,028           107,062      
Lease Term 10 years 1 month 6 days           6 years      
Aggregate Purchase Price $ 20,500           $ 17,000      
Aggregate Annualized GAAP Rent $ 3,000           1,400      
Aggregate Debt Issued or Assumed             $ 9,900      
Fort Lauderdale, FL                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²           119,224        
Lease Term           9 years        
Aggregate Purchase Price           $ 23,900        
Aggregate Annualized GAAP Rent           2,000        
Aggregate Debt Issued or Assumed           $ 14,100        
King of Prussia, PA                    
Business Acquisition [Line Items]                    
Aggregate Square Footage | ft²         103,334          
Lease Term         15 years          
Aggregate Purchase Price         $ 25,700          
Acquisition Expenses         200          
Aggregate Annualized GAAP Rent         2,200          
Aggregate Debt Issued or Assumed         $ 14,800          
Minimum                    
Business Acquisition [Line Items]                    
Lease Term               1 year 1 year  
Maximum                    
Business Acquisition [Line Items]                    
Lease Term               11 years 3 months 7 years 8 months 12 days  
New Fixed Rate Mortgage Notes Payable                    
Business Acquisition [Line Items]                    
Noncash or part noncash acquisition, debt assumed               $ 54,900    
New Fixed Rate Mortgage Notes Payable | Minimum | Philadelphia, PA                    
Business Acquisition [Line Items]                    
Debt instrument, interest rate, stated percentage     3.75%              
New Fixed Rate Mortgage Notes Payable | Maximum | Maitland, Florida                    
Business Acquisition [Line Items]                    
Debt instrument, interest rate, stated percentage   3.89%                
Interest Rate Swap                    
Business Acquisition [Line Items]                    
Interest rate swap assumed       1.80%            
Fixed interest rate risk exposure       3.55%            
Interest Rate Swap | Conshohocken, Pennsylvania                    
Business Acquisition [Line Items]                    
Noncash or part noncash acquisition, debt assumed       $ 11,200            
Derivative asset       $ 40       $ 300    
Interest Rate Swap | New Fixed Rate Mortgage Notes Payable                    
Business Acquisition [Line Items]                    
Debt instrument, interest rate, stated percentage               3.545%