Collateral Positions (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Collateral Positions
Assets Pledged	$ 8,135,335	$ 8,145,197
Collateral Held	253,993	504,062
Derivative Hedging Instruments
Collateral Positions
Assets Pledged	16,244	28,161
Collateral Held	0	0
Derivative Hedging Instruments \| Agency MBS
Collateral Positions
Assets Pledged	16,244	21,756
Collateral Held	0	0
Derivative Hedging Instruments \| Cash
Collateral Positions
Assets Pledged	0	6,405
Collateral Held	0	0
Repurchase Agreement Borrowings
Collateral Positions
Assets Pledged	8,119,091	8,117,036
Collateral Held	0	0
Repurchase Agreement Borrowings \| Agency MBS
Collateral Positions
Assets Pledged	2,531,106	2,705,754
Collateral Held	0	0
Repurchase Agreement Borrowings \| Legacy Non-Agency MBS
Collateral Positions
Assets Pledged	1,897,016	1,652,983
Collateral Held	0	0
Non-Agency MBS pledged as collateral in connection with contemporaneous repurchase and reverse repurchase agreements entered into with a single counterparty	329,800	688,100
Repurchase Agreement Borrowings \| RPL/NPL MBS
Collateral Positions
Assets Pledged	733,409	726,540
Collateral Held	0	0
Repurchase Agreement Borrowings \| U.S. Treasury securities
Collateral Positions
Assets Pledged	220,814	472,095
Collateral Held	0	0
Repurchase Agreement Borrowings \| CRT securities
Collateral Positions
Assets Pledged	590,551	595,900
Collateral Held	0	0
Repurchase Agreement Borrowings \| MSR related assets
Collateral Positions
Assets Pledged	432,468	482,158
Collateral Held	0	0
Repurchase Agreement Borrowings \| Residential whole loans
Collateral Positions
Assets Pledged	1,706,627	1,474,704
Collateral Held	0	0
Repurchase Agreement Borrowings \| Cash
Collateral Positions
Assets Pledged	7,100	6,902
Collateral Held	0	0
Reverse Repurchase Agreements
Collateral Positions
Assets Pledged	0	0
Collateral Held	253,993	504,062
Reverse Repurchase Agreements \| U.S. Treasury securities
Collateral Positions
Assets Pledged	0	0
Collateral Held	$ 253,993	$ 504,062

-- None. No documentation exists for this element. --

No definition available.

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- Definition

Represents the non-agency MBS pledged as collateral in connection with contemporaneous repurchase and reverse repurchase agreements entered into with a single counterparty.

+ References

No definition available.

+ Details

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- Definition

The carrying amount, as of the date of the latest financial statement presented, of all assets that are pledged as collateral for the payment of the related debt obligation primarily arising from secured borrowings, repurchase agreements or other current or potential obligations, where the secured party does not have the right by contract or custom to sell or re-pledge the collateral and therefore are not reclassified and separately reported in the statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

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- Definition

Fair value of the securities pledged as collateral against securities loaned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226013-175313

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