Repurchase Agreements - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2016 USD ($) agreement counterparty	Dec. 31, 2015 USD ($) agreement counterparty
Concentration Risk [Line Items]
Number of MRAs \| agreement	37	38
Number of counterparties with repurchase agreements outstanding \| counterparty	26	26
Counterparty Concentration Risk \| Repurchase Agreement Borrowings
Concentration Risk [Line Items]
Percentage of portfolio invested	43.50%	53.48%
Minimum \| Counterparty Concentration Risk \| Repurchase Agreement Borrowings \| Five Repurchase Agreement Counterparties
Concentration Risk [Line Items]
Percentage of portfolio invested	5.00%
Minimum \| Counterparty Concentration Risk \| Repurchase Agreement Borrowings \| Eight Repurchase Agreement Counterparties
Concentration Risk [Line Items]
Percentage of portfolio invested	5.00%
Maximum
Concentration Risk [Line Items]
Ratio of indebtedness to net capital	12
Maximum \| Counterparty Concentration Risk \| Repurchase Agreement Borrowings \| Five Repurchase Agreement Counterparties
Concentration Risk [Line Items]
Percentage of portfolio invested	10.00%
Maximum \| Counterparty Concentration Risk \| Repurchase Agreement Borrowings \| One Repurchase Agreement Counterparty
Concentration Risk [Line Items]
Percentage of portfolio invested	10.50%
Maximum \| Counterparty Concentration Risk \| Repurchase Agreement Borrowings \| Eight Repurchase Agreement Counterparties
Concentration Risk [Line Items]
Percentage of portfolio invested	10.00%
Carrying Value
Concentration Risk [Line Items]
Repurchase Agreements \| $	$ 9,923,859	$ 11,570,481

Repurchase Agreements, Number Of Counterparties with Outstanding Borrowings

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Repurchase Agreements, Number of Master Repurchase Agreements

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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.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6351-108592

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-Name Accounting Standards Codification
-Topic 825
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-Publisher FASB
-Name Accounting Standards Codification
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Indebtedness divided by net capital.

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- Definition

Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 825
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