| 
           Real Estate and Intangible Assets - Fair Value of Acquired Assets and Liabilities Assumed Related to Properties Acquired (Parenthetical) (Detail) (USD $) 
         | 
        9 Months Ended | |
|---|---|---|
| 
           Sep. 30, 2014
 
          2014 New Real Estate Activity [Member] 
         | 
        
           Sep. 30, 2013
 
          2013 New Real Estate Activity [Member] 
         | 
      |
| Business Acquisition Purchase Price Allocation [Line Items] | ||
| Acquisition costs were direct costs incurred related to leases | $ 17,558 | $ 13,377 | 
| X | ||||||||||
| 
             
- Details 
          
  | 
        
| X | ||||||||||
| 
             
- Definition 
          The capitalized costs incurred during the period (excluded from amortization) to purchase, lease or otherwise acquire an unproved property, including costs of lease bonuses and options to purchase or lease properties, the portion of costs applicable to minerals when land including mineral rights is purchased in fee, brokers' fees, recording fees, legal costs, and other costs incurred in acquiring properties. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  |