Quarterly report pursuant to Section 13 or 15(d)

Real Estate and Intangible Assets - Fair Value of Acquired Assets and Liabilities Assumed (Detail)

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Real Estate and Intangible Assets - Fair Value of Acquired Assets and Liabilities Assumed (Detail) (USD $)
In Thousands, unless otherwise specified
6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Loans At Acquisition Date [Line Items]    
Total Purchase Price $ 36,738 $ 42,565
Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price 5,650  
Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price 13,388  
Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price 14,450  
Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price   10,775
Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price   7,100
New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price   13,333
Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price   7,320
Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Total Purchase Price   4,037
Customer Relationships [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,702 2,601
Customer Relationships [Member] | Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 259  
Customer Relationships [Member] | Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 627  
Customer Relationships [Member] | Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 816  
Customer Relationships [Member] | Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   499
Customer Relationships [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   499
Customer Relationships [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   903
Customer Relationships [Member] | Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   375
Customer Relationships [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   325
Above Market Leases [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   160
Above Market Leases [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   47
Above Market Leases [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   113
Below Market Leases [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   107
Below Market Leases [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   107
Land [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 3,144 4,496
Land [Member] | Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,627  
Land [Member] | Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 457  
Land [Member] | Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,060  
Land [Member] | Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   706
Land [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   212
Land [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   1,658
Land [Member] | Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   1,378
Land [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   542
Building [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 21,803 24,555
Building [Member] | Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 2,735  
Building [Member] | Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 9,721  
Building [Member] | Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 9,347  
Building [Member] | Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   6,551
Building [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   4,743
Building [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   7,511
Building [Member] | Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   3,894
Building [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   1,856
Tenant Improvements [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 2,262 4,094
Tenant Improvements [Member] | Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 282  
Tenant Improvements [Member] | Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 808  
Tenant Improvements [Member] | Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,172  
Tenant Improvements [Member] | Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   1,307
Tenant Improvements [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   329
Tenant Improvements [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   1,235
Tenant Improvements [Member] | Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   626
Tenant Improvements [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   597
In-place Leases [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 3,016 3,831
In-place Leases [Member] | Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 558  
In-place Leases [Member] | Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,097  
In-place Leases [Member] | Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,361  
In-place Leases [Member] | Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   804
In-place Leases [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   940
In-place Leases [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   1,122
In-place Leases [Member] | Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   574
In-place Leases [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   391
Leasing Costs [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 1,561 2,935
Leasing Costs [Member] | Egg Harbor Township, NJ [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 189  
Leasing Costs [Member] | Brookwood, AL [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 678  
Leasing Costs [Member] | Blaine, MN [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired 694  
Leasing Costs [Member] | Ashburn, VA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   908
Leasing Costs [Member] | Ottumwa, IA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   484
Leasing Costs [Member] | New Albany, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   857
Leasing Costs [Member] | Columbus, GA [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   473
Leasing Costs [Member] | Columbus, OH [Member]
   
Loans At Acquisition Date [Line Items]    
Fair value of acquired assets and liabilities assumed related to the properties acquired   $ 213