Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
6 Months Ended
Jun. 30, 2014
segment
Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]    
Allowance for doubtful accounts $ 5,400,000 $ 4,600,000
Assets 7,500,907,000 7,231,045,000
Liabilities 4,238,559,000 4,113,011,000
Number of segments 1  
Accounts receivable 18,800,000 14,300,000
Provision for losses 10,800,000 9,600,000
Accrued rental revenue receivables 42,000,000 35,300,000
Allowance for loan losses 0 0
Loan placed on non accrual status, past due days 60 days  
Provision for income taxes 0  
Mortgages
   
Summary Of Significant Accounting Policies [Line Items]    
Loans on non accruals status 0 0
Notes
   
Summary Of Significant Accounting Policies [Line Items]    
Loans on non accruals status 0 0
Special Purpose Entity
   
Summary Of Significant Accounting Policies [Line Items]    
Assets 6,300,000,000 6,100,000,000
Liabilities $ 3,300,000,000 $ 3,800,000,000