Debt (Summary of Outstanding and Carrying Value of Collateral by Asset Type) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Outstanding Balance	$ 8,059,802	$ 10,425,778
Other Debt [Member]
Debt Instrument [Line Items]
Outstanding Balance	33,463
Collateral Carrying Value	66,694
Other Debt [Member] | Loans held for investment [Member]
Debt Instrument [Line Items]
Outstanding Balance	9,245
Collateral Carrying Value	20,190
Other Debt [Member] | Intercompany mortgage loans [Member]
Debt Instrument [Line Items]
Outstanding Balance	2,586
Collateral Carrying Value	7,356
Other Debt [Member] | CMBS [Member]
Debt Instrument [Line Items]
Outstanding Balance	21,632
Collateral Carrying Value	$ 39,148