Derivatives TBA securities (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		$ 4,845	$ 6,563
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest rate swaps
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	[1]	0	324
Derivative, Notional Amount	[2]	3,880,000	4,515,000
Not Designated as Hedging Instrument, Economic Hedge [Member] | Eurodollar futures
Derivative [Line Items]
Derivative, Notional Amount		6,000,000	0
Long position | Not Designated as Hedging Instrument, Trading | TBA securities
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		2,066	6,239
Derivative, Notional Amount		395,000	860,000
Cost Basis,TBA		(393,808)	(882,230)
Market value, TBA		(395,874)	(888,469)	[3]
Net carrying value, TBA	[4]	(2,066)	(6,239)
Short position | Not Designated as Hedging Instrument, Economic Hedge [Member] | TBA securities
Derivative [Line Items]
Derivative, Notional Amount		500,000	0
Cost Basis,TBA		(518,643)	0
Market value, TBA		(519,082)	0
Net carrying value, TBA		$ (439)	$ 0

[1] Amounts shown as of September 30, 2019 and December 31, 2018 are net of $(44,140) paid and $8,424 received, respectively, in variation margin which is recorded on the Company’s consolidated balance sheets within “restricted cash.” As of September 30, 2019, all of the Company’s interest rate swap agreements are centrally cleared through the CME. Please refer to Note 1 for information regarding the exchange of variation margin being legally considered as settlement of the derivative as opposed to a pledge of collateral. The amount shown as of December 31, 2018 is the unsettled fair value of the instruments subject to bilateral agreements and not centrally cleared through the CME as of that date.

[2] The notional amounts include $0 and $775,000 of forward starting pay-fixed interest rate swaps as of September 30, 2019 and December 31, 2018, respectively.

[3] (1) Implied market value represents the estimated fair value of the underlying Agency MBS as if settled as of the date indicated.

[4] Net carrying value is the amount included on the consolidated balance sheets within “derivative assets (liabilities)” and represents the difference between the implied market value and the implied cost basis of the TBA security as of the date indicated.