Collateral Positions (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Collateral Positions
Assets Pledged	$ 8,997,518	$ 8,145,197
Collateral Held	0	504,062
Derivative Hedging Instruments
Collateral Positions
Assets Pledged	2,877	28,161
Collateral Held	0	0
Derivative Hedging Instruments \| Agency MBS
Collateral Positions
Assets Pledged	2,877	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	8,994,641	8,117,036
Collateral Held	0	0
Repurchase Agreement Borrowings \| Agency MBS
Collateral Positions
Assets Pledged	2,792,396	2,705,754
Collateral Held	0	0
Repurchase Agreement Borrowings \| Legacy Non-Agency MBS
Collateral Positions
Assets Pledged	2,075,540	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		688,100
Repurchase Agreement Borrowings \| RPL/NPL MBS
Collateral Positions
Assets Pledged	1,161,568	726,540
Collateral Held	0	0
Repurchase Agreement Borrowings \| U.S. Treasury securities
Collateral Positions
Assets Pledged	0	472,095
Collateral Held	0	0
Repurchase Agreement Borrowings \| CRT securities
Collateral Positions
Assets Pledged	504,931	595,900
Collateral Held	0	0
Repurchase Agreement Borrowings \| MSR related assets
Collateral Positions
Assets Pledged	565,272	482,158
Collateral Held	0	0
Repurchase Agreement Borrowings \| Residential whole loans
Collateral Positions
Assets Pledged	1,888,445	1,474,704
Collateral Held	0	0
Repurchase Agreement Borrowings \| Cash
Collateral Positions
Assets Pledged	6,489	6,902
Collateral Held	0	0
Reverse Repurchase Agreements
Collateral Positions
Assets Pledged	0	0
Collateral Held	0	504,062
Reverse Repurchase Agreements \| U.S. Treasury securities
Collateral Positions
Assets Pledged	0	0
Collateral Held	0	$ 504,062
Loan Securitization
Collateral Positions
Fair value of securities pledged as collateral under repurchase agreements	$ 27,000

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

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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://fasb.org/us-gaap/role/ref/legacyRef
-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=109249958&loc=SL6224234-111729

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- Definition

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 12
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