Derivatives Effect of Derivatives on Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	$ 4,175	$ (2,281)	$ 4,533	$ (4,941)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	6,844	4,745	9,580	6,912
Unrealized Gain (Loss) on Derivatives	6,583	(11,718)	40,040	(14,557)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	4,175	(2,281)	4,533	(4,941)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	11,303	(11,570)	59,232	14,451
Unrealized Gain (Loss) on Derivatives	1,407	2,081	3,527	(19,749)
Interest Rate Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	0	0	0	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	0
Unrealized Gain (Loss) on Derivatives	1,219	(135)	6,541	(563)
Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	0	0	0	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(4,109)	31,177	(47,254)	6,887
Unrealized Gain (Loss) on Derivatives	113	(12,077)	8,072	17,433
Credit Default Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	0	0	0	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	(470)	(1,648)	(513)
Unrealized Gain (Loss) on Derivatives	0	274	1,528	(183)
Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	0	0	0	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	20	33	9	261
Unrealized Gain (Loss) on Derivatives	(25)	0	0	7
Short [Member] \| US Treasury Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss) on periodic interest settlements of interest rate swaps, net	0	0	0	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(370)	(14,425)	(759)	(14,174)
Unrealized Gain (Loss) on Derivatives	$ 3,869	$ (1,861)	$ 20,372	$ (11,502)

MTGE Investment Corp. 10-Q