Fair Value Measurements (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain (loss) on derivatives	$ (2,534)	$ (7,402)	$ (1,100)
Unrealized gain (loss) on marketable securities	4,946	127	(332)
Future [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accumulated OCI into Interest Expense, Net			0
Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Net	(1,169)	(7,766)	4,347
Unrealized gain (loss) on derivatives	(2,534)	(7,402)	(1,100)
Unrealized gain (loss) on marketable securities	4,946	127	(332)
Realized gain (loss) on marketable securities	0	1,968	5,779
Accumulated OCI into Interest Expense, Liabilities	0	0	100
Accumulated OCI into Interest Expense, Net	0	0	100
Fair Value Measurements Recurring [Member] | Interest Rate Floor [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain (loss) on derivatives	611	(7,603)	0
Accumulated OCI into Interest Expense, Net	0	0	0
Fair Value Measurements Recurring [Member] | Interest Rate Cap [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain (loss) on derivatives	(535)	(2,038)	(484)
Accumulated OCI into Interest Expense, Net	0	0	100
Fair Value Measurements Recurring [Member] | Credit Default Swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain (loss) on derivatives	(2,574)	2,630	(616)
Realized Gain (Loss) on Derivatives	(3,269)	(2,459)	0
Accumulated OCI into Interest Expense, Net	0	0	0
Fair Value Measurements Recurring [Member] | Future [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gain (loss) on derivatives	(36)	(391)	0
Realized Gain (Loss) on Derivatives	(312)	0	0
Accumulated OCI into Interest Expense, Net	0	0
Fair Value Measurements Recurring [Member] | Derivative Liabilities [Member] | Credit Default Swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Liabilities	0	0	(699)
Accumulated OCI into Interest Expense, Liabilities	0	0	0
Fair Value Measurements Recurring [Member] | Derivative Liabilities [Member] | Put Option [Member] | Short [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Liabilities	0	1,002	1,111
Accumulated OCI into Interest Expense, Liabilities	0	0	0
Fair Value Measurements Recurring [Member] | Derivative Liabilities [Member] | Call Option [Member] | Short [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Liabilities	0	1,470	429
Accumulated OCI into Interest Expense, Liabilities	0	0	0
Fair Value Measurements Recurring [Member] | Non Derivative Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Liabilities	0	2,550	841
Accumulated OCI into Interest Expense, Liabilities	0	0	0
Fair Value Measurements Recurring [Member] | Non Derivative Liability [Member] | Equity Securities [Member] | Short [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Liabilities	0	78	0
Accumulated OCI into Interest Expense, Liabilities	0	0	0
Fair Value Measurements Recurring [Member] | Derivative assets [Member] | Interest Rate Floor [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	611	(7,603)	0
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Derivative assets [Member] | Interest Rate Cap [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	(535)	(2,038)	(484)
Accumulated OCI into Interest Expense, Assets	0	0	100
Fair Value Measurements Recurring [Member] | Derivative assets [Member] | Credit Default Swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	(5,843)	171	0
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Derivative assets [Member] | Future [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	(348)	(391)	0
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Derivative assets [Member] | Put Option [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	0	26	0
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Derivative assets [Member] | Call Option [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	0	(1,717)	(3,942)
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Non Derivative Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	(1,169)	(10,316)	3,506
Accumulated OCI into Interest Expense, Assets	0	0	100
Fair Value Measurements Recurring [Member] | Non Derivative Assets [Member] | US Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	0	314	0
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Non Derivative Assets [Member] | 8880 American Depositary Receipts [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	0	(150)	0
Accumulated OCI into Interest Expense, Assets	0	0	0
Fair Value Measurements Recurring [Member] | Non Derivative Assets [Member] | Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gain or (Loss) Recognized in Income, Assets	4,946	1,072	7,932
Accumulated OCI into Interest Expense, Assets	$ 0	$ 0	$ 0