Summary of Significant Accounting Policies - Narrative (Details)
9 Months Ended
Sep. 30, 2016
USD ($)
segment
Dec. 31, 2015
USD ($)
Summary Of Significant Accounting Policies [Line Items]    
Net assets $ 7,811,000,000 $ 7,891,039,000
Net liabilities $ 4,045,065,000 4,429,165,000
Number of segments | segment 1  
Reserves for uncollectible amounts $ 14,700,000 11,500,000
Accounts receivable 32,800,000 26,300,000
Reserve for losses 12,200,000 12,200,000
Deferred rental revenue receivables 79,800,000 68,000,000
Lender reserves surrendered 2,300,000  
Provision for income taxes 0  
Special Purpose Entity    
Summary Of Significant Accounting Policies [Line Items]    
Net assets 3,080,000,000 4,570,000,000
Net liabilities $ 2,340,000,000 $ 3,190,000,000