Financing Arrangements, Portfolio Investments - Assets Pledged as Collateral (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial Instruments Owned and Pledged as Collateral [Line Items]
Outstanding Borrowings	$ 1,543,577	$ 1,276,918
Fair Value of Collateral Pledged	1,784,191	1,453,699
Amortized Cost Of Collateral Pledged	1,672,486	1,368,115
Consolidated K-Series
Financial Instruments Owned and Pledged as Collateral [Line Items]
K-series net carrying value	657,600	468,000
Agency ARMs RMBS
Financial Instruments Owned and Pledged as Collateral [Line Items]
Outstanding Borrowings	67,648	86,349
Fair Value of Collateral Pledged	70,747	90,343
Amortized Cost Of Collateral Pledged	73,290	92,586
Agency Fixed-rate RMBS
Financial Instruments Owned and Pledged as Collateral [Line Items]
Outstanding Borrowings	857,582	842,474
Fair Value of Collateral Pledged	907,610	890,359
Amortized Cost Of Collateral Pledged	940,994	902,744
Non-Agency RMBS
Financial Instruments Owned and Pledged as Collateral [Line Items]
Outstanding Borrowings	88,730	38,160
Fair Value of Collateral Pledged	117,958	51,841
Amortized Cost Of Collateral Pledged	118,414	50,693
CMBS
Financial Instruments Owned and Pledged as Collateral [Line Items]
Outstanding Borrowings	529,617	309,935
Fair Value of Collateral Pledged	687,876	421,156
Amortized Cost Of Collateral Pledged	539,788	322,092
CMBS \| Consolidated K-Series
Financial Instruments Owned and Pledged as Collateral [Line Items]
K-series net carrying value	$ 319,200	$ 377,500

Amortized Cost Of Collateral Pledged.

No definition available.

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- Definition

Represents the aggregate carrying value of the investment in the multi-family loans held in securitization trusts.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

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

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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