Derivative Instruments and Hedging (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 30, 2015	Apr. 30, 2015	Feb. 28, 2015	Aug. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	$ (7,402,000)	$ (1,100,000)	$ (8,315,000)
Derivative assets, net	3,435,000	182,000
Indebtedness, net	3,840,617,000	1,943,133,000
Mortgage Loans, Variable Interest, 2015 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Indebtedness, net	2,200,000,000
Conventional Mortgage Loan [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Indebtedness, net	812,400,000
Interest Rate Floor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative	$ 6,000,000,000
Derivative, Floor Price	(0.25%)
Higher fixed interest rate	0.00%
Interest Rate Cap Two [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Payments of derivative issuance costs		666,000
Interest Rate Cap Two [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative		$ 947,100,000
Lower fixed interest rate		2.00%
Higher fixed interest rate		3.69%
Interest Rate Cap One [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative	$ 2,200,000,000
Lower fixed interest rate	1.50%
Higher fixed interest rate	3.00%
Payments of derivative issuance costs	$ 2,200,000
Credit Default Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivative				$ 50,000,000	$ 45,000,000	$ 45,000,000	$ 100,000,000
Transaction cost	4,700,000
Change in market value of credit default swap	250,000
Unrealized gain (loss) on derivatives	2,600,000	$ (616,000)	$ (1,937,000)
Derivative upfront cost				$ 500,000	$ 1,100,000	$ 1,600,000	$ 8,200,000
Credit Default Swaps [Member] | Marketable Securities and Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of credit derivatives, net	1,100,000	(184,000)
CMBX Tranche [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized loss on derivative	2,500,000
Foreign Exchange Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivatives	(391,000)
Derivative assets, net	234,000
Foreign Exchange Option [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Payments of derivative issuance costs	743,000
Investment Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative assets, net		654,000
Derivative liabilities		$ 997,000
Interest Rate Floor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative assets, net	1,700,000
Interest Rate Floor [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Payments of derivative issuance costs	9,400,000
Interest Rate Cap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative assets, net	$ 360,000