Debt - Summary of Debt (Details) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2018
Dec. 31, 2017
May 31, 2014
Debt Instrument [Line Items]      
Total debt, net $ 1,832,132 $ 1,712,846  
Revolving Credit Facility      
Debt Instrument [Line Items]      
Total debt, gross 346,500    
Term Loan      
Debt Instrument [Line Items]      
Deferred financing costs, net (300) (700)  
Master Trust Notes      
Debt Instrument [Line Items]      
Debt discount, net 0 (36,188)  
Deferred financing costs, net (4,588) (24,010)  
Total debt, net 165,566 2,188,306  
Convertible Notes      
Debt Instrument [Line Items]      
Deferred financing costs, net (6,200) (8,000) $ (19,600)
Continuing and discontinuing operations      
Debt Instrument [Line Items]      
Total debt, gross 1,869,646 3,740,651  
Debt discount, net (20,042) (61,399)  
Deferred financing costs, net (17,472) (39,572)  
Total debt, net $ 1,832,132 3,639,680  
Continuing and discontinuing operations | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 5.30%    
Weighted average stated rate 3.95%    
Weighted average maturity 3 years 6 months 21 days    
Continuing and discontinuing operations | Revolving Credit Facility      
Debt Instrument [Line Items]      
Total debt, gross $ 346,500 112,000  
Continuing and discontinuing operations | Revolving Credit Facility | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 4.49%    
Weighted average stated rate 3.32%    
Weighted average maturity 9 months 18 days    
Continuing and discontinuing operations | Term Loan      
Debt Instrument [Line Items]      
Total debt, gross $ 0 0  
Continuing and discontinuing operations | Term Loan | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 0.00%    
Weighted average stated rate 0.00%    
Weighted average maturity 3 months 18 days    
Continuing and discontinuing operations | Master Trust Notes      
Debt Instrument [Line Items]      
Total debt, gross $ 170,154 2,248,504  
Continuing and discontinuing operations | Master Trust Notes | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 5.50%    
Weighted average stated rate 5.27%    
Weighted average maturity 5 years 6 months    
Continuing and discontinuing operations | CMBS      
Debt Instrument [Line Items]      
Total debt, gross $ 276,124 332,647  
Continuing and discontinuing operations | CMBS | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 5.73%    
Weighted average stated rate 5.51%    
Weighted average maturity 4 years 11 months 26 days    
Continuing and discontinuing operations | Related Party Notes Payable      
Debt Instrument [Line Items]      
Total debt, gross $ 29,368 0  
Continuing and discontinuing operations | Related Party Notes Payable | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 0.99%    
Weighted average stated rate 1.00%    
Weighted average maturity 9 years 4 months 24 days    
Continuing and discontinuing operations | Convertible Notes      
Debt Instrument [Line Items]      
Total debt, gross $ 747,500 747,500  
Continuing and discontinuing operations | Convertible Notes | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 5.32%    
Weighted average stated rate 3.28%    
Weighted average maturity 1 year 9 months 18 days    
Continuing and discontinuing operations | Senior Unsecured Notes      
Debt Instrument [Line Items]      
Total debt, gross $ 300,000 $ 300,000  
Continuing and discontinuing operations | Senior Unsecured Notes | Weighted Average      
Debt Instrument [Line Items]      
Weighted average effective interest rate 4.65%    
Weighted average stated rate 4.45%    
Weighted average maturity 8 years 2 months 12 days