Debt - Summarized Debt (Details) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended 9 Months Ended 9 Months Ended 9 Months Ended 9 Months Ended 9 Months Ended 9 Months Ended
Sep. 30, 2014
Dec. 31, 2013
Sep. 30, 2014
Weighted Average
Sep. 30, 2014
Revolving credit facilities
Dec. 31, 2013
Revolving credit facilities
Sep. 30, 2014
Revolving credit facilities
Weighted Average
Sep. 30, 2014
Master trust notes
Dec. 31, 2013
Master trust notes
Sep. 30, 2014
Master trust notes
Weighted Average
Sep. 30, 2014
CMBS - fixed-rate
Dec. 31, 2013
CMBS - fixed-rate
Sep. 30, 2014
CMBS - fixed-rate
Weighted Average
Sep. 30, 2014
CMBS - variable-rate
Dec. 31, 2013
CMBS - variable-rate
Sep. 30, 2014
CMBS - variable-rate
Weighted Average
Sep. 30, 2014
Unsecured fixed rate promissory note
Dec. 31, 2013
Unsecured fixed rate promissory note
Sep. 30, 2014
Unsecured fixed rate promissory note
Weighted Average
Sep. 30, 2014
Convertible Notes
Dec. 31, 2013
Convertible Notes
Sep. 30, 2014
Convertible Notes
Weighted Average
Debt Instrument [Line Items]                                          
Weighted average effective interest rates     5.40% [1]           5.81% [1]     5.34% [1]     3.50% [1],[2]     9.12% [1]     4.80% [1]
Weighted average stated interest rate     5.06% [3]     2.81% [3]     5.35% [3]     5.84% [3]     3.28% [2],[3]     7.00% [3]     3.28% [3]
Weighted Average Maturity     4 years 8 months 16 days [4]     1 year 8 months 23 days [4]     6 years 9 months 7 days [4]     3 years 1 month 21 days [4]     2 years 4 months 17 days [2],[4]     7 years 3 months 4 days [4]     5 years 6 months 18 days [4]
Long-term debt, gross $ 4,058,352 $ 3,776,549   $ 125,436 $ 35,120   $ 1,204,787 $ 1,241,437   $ 1,868,518 $ 2,387,532   $ 110,771 [2] $ 111,018 [2]   $ 1,340 $ 1,442   $ 747,500 $ 0  
Unamortized net debt (discount) or premium (50,524) 1,669                                      
Total debt, net $ 4,007,828 $ 3,778,218                                      
[1] The effective interest rates include amortization of debt discount/premium and amortization of deferred financing costs calculated for the three months ended September 30, 2014.
[2] Variable-rate notes are predominately hedged with interest rate swaps (see Note 6).
[3] Represents the weighted average stated interest rate based on the outstanding principal balance as of September 30, 2014.
[4] Represents the weighted average maturity based on the outstanding principal balance as of September 30, 2014.