Derivative Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components of the gain on Linked Transactions
Change in fair value of Linked Transactions included in earnings	$ 1,111	$ 9,593	$ (14,855)
Linked Transactions
Linked Repurchase Agreements
Balance	102,737	35,271
Weighted Average Interest Rate (as a percent)	1.73%	1.63%
Linked MBS
Fair Value	130,790	47,828
Amortized Cost	126,497	43,817
Par/Current Face	134,430	52,277
Weighted Average Coupon Rate (as a percent)	3.96%	4.28%
MBS, accrued interest receivable	210	185
MBS, accrued interest payable	82	38
Components of the gain on Linked Transactions
Interest income attributable to MBS underlying Linked Transactions	3,869	5,089	25,592
Interest expense attributable to linked repurchase agreement borrowings underlying Linked Transactions	(925)	(1,113)	(4,794)
Change in fair value of Linked Transactions included in earnings	281	8,634	(17,783)
Unrealized net gains and net interest income from Linked Transactions	3,225	12,610	3,015
Linked Transactions \| Rated AA
Linked MBS
Fair Value	9,054	13,588
Amortized Cost	8,486	12,817
Par/Current Face	8,790	13,192
Weighted Average Coupon Rate (as a percent)	5.00%	5.00%
Linked Transactions \| Rated A
Linked MBS
Fair Value	2,574	3,075
Amortized Cost	2,077	2,548
Par/Current Face	2,682	3,342
Weighted Average Coupon Rate (as a percent)	1.27%	0.76%
Linked Transactions \| Rated BBB
Linked MBS
Fair Value	7,436	8,299
Amortized Cost	6,564	7,226
Par/Current Face	7,903	8,847
Weighted Average Coupon Rate (as a percent)	2.21%	2.55%
Linked Transactions \| Rated BB
Linked MBS
Fair Value	6,476	7,365
Amortized Cost	6,067	6,854
Par/Current Face	6,608	7,593
Weighted Average Coupon Rate (as a percent)	2.47%	2.75%
Linked Transactions \| Rated D
Linked MBS
Fair Value	13,740	15,501
Amortized Cost	11,834	14,372
Par/Current Face	16,216	19,303
Weighted Average Coupon Rate (as a percent)	5.20%	5.80%
Linked Transactions \| Not Rated
Linked MBS
Fair Value	91,510
Amortized Cost	91,469
Par/Current Face	92,231
Weighted Average Coupon Rate (as a percent)	3.97%
Linked Transactions \| Within 30 days
Linked Repurchase Agreements
Balance	93,835	13,672
Weighted Average Interest Rate (as a percent)	1.76%	1.57%
Linked Transactions \| Over 30 days to 90 days
Linked Repurchase Agreements
Balance	$ 8,902	$ 21,599
Weighted Average Interest Rate (as a percent)	1.44%	1.66%

The interest rate for investments that have an interest rate. For fixed rate investments, this indicates the fixed interest rate. If the investment has a variable interest rate, the rate stated here may be the rate that is currently relevant. In this case the "Investment, Interest Rate is Current Rate for Variable Rate Investment Flag", "Investment, Interest Rate is Discount Rate at Purchase Flag", "Investment, Interest Rate Reflects Current Yield Flag" should be used. If one of these flags are not appropriate to explain the interest rate that is indicated, then a new flag should be added or an explanation should be included in "Investment, Additional Information".

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 12

-Sentence Column A

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- Definition

Represents the interest expense on mortgage backed securities in linked transactions (MBS purchase and repurchase financing) accounted for as derivative forward contracts.

+ References

No definition available.

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- Definition

Represents interest payable, derived from securities backed by a pool of mortgages or trust deeds.

+ References

No definition available.

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- Definition

Represents interest receivable, derived from securities backed by a pool of mortgages or trust deeds.

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No definition available.

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- Definition

Represents the amortized cost of mortgage backed securities in linked transactions (MBS purchase and repurchase financing) accounted for as derivative forward contracts.

+ References

No definition available.

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- Definition

Represents the fair value of mortgage backed securities in linked transactions (MBS purchase and repurchase financing) accounted for as derivative forward contracts.

+ References

No definition available.

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- Definition

Represents the principal balance of mortgage backed securities in linked transactions (MBS purchase and repurchase financing) accounted for as derivative forward contracts.

+ References

No definition available.

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- Definition

Represents the carrying value as of the balance sheet date of repurchase financing agreements related to MBS purchases, which are accounted for as forward purchase agreements and are netted against the carrying value of the associated MBS.

+ References

No definition available.

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- Definition

Represents unrealized net (losses)/gains and net interest income from linked transactions of the entity.

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No definition available.

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Interest rate on the amount to be repaid to the counterparty to the repurchase agreement when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under the repurchase agreement exceeds 10 percent of total assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph m

-Subparagraph 1

-Article 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(ii))

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- Definition

Amount of operating interest income, including amortization and accretion of premiums and discounts, on securitized, pass-through debt securities collateralized by real estate mortgage loans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.2)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Mortgage-Backed Securities

-URI http://asc.fasb.org/extlink&oid=6517959

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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