Quarterly report pursuant to Section 13 or 15(d)

Mortgage Notes Payable and Line of Credit - Additional Information (Detail)

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Mortgage Notes Payable and Line of Credit - Additional Information (Detail) (USD $)
 1 Months Ended 6 Months Ended 12 Months Ended
Dec. 31, 2010
Jun. 30, 2013
Mortgages
Property
Dec. 31, 2012
Jan. 31, 2012
Jun. 30, 2013
Mortgage Notes Payable [Member]
Mortgages
Dec. 31, 2010
Senior Secured Revolving Credit Facility [Member]
Jun. 30, 2013
Senior Secured Revolving Credit Facility [Member]
Jun. 30, 2013
Revolving Credit Facility [Member]
Jun. 30, 2013
Letter of Credit [Member]
Proforma Debt Instrument [Line Items]                  
Number of fixed-rate mortgage notes payable         31        
Weighted average interest rate on all debt outstanding   5.54%     5.62%        
Number of properties collateralized in fixed-rate mortgage notes payable   65              
Number of long-term mortgages issued   1              
Fair value of fixed-rate mortgage notes payable outstanding   $ 359,400,000              
Carrying value of fixed-rate mortgage notes payable outstanding   359,240,000 359,185,000            
Line of credit, outstanding 50,000,000         50,000,000 11,200,000    
Line of credit, maturity date           Dec. 28, 2013      
Standby letters of credit sublimit 20,000,000                
Line of credit, maximum borrowing capacity amended       75,000,000          
Line of credit, variable spread on interest rate 3.00%                
Line of credit, annual maintenance fees, percentage   0.25%              
Number of properties pledged as collateral under Line of credit   15              
Line of credit covenant limit of distributions to shareholders percentage       95.00%          
Line of credit at an interest rate   3.00%           3.00%  
Letters of credit, outstanding                 5,600,000
Line of credit facility, maximum additional amount drawn   $ 26,300,000