Repurchase Agreements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	$ 3,013,110	$ 3,580,754
Repurchage agreement, Weighted Average Interest Rate	0.55%	0.61%
Fair Value of Collateral Pledged	3,274,597	3,890,066
Deferred Costs	0	(243)
Repurchase Agreement Counterparty, Weighted Average Maturity of Agreements	144 days	114 days
Collateralized Mortgage Obligations [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	9,834	20,651
Repurchage agreement, Weighted Average Interest Rate	1.51%	1.59%
Fair Value of Collateral Pledged	11,000	19,686
Residential Mortgage Backed Securities [Member] \| Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	1,977,338	2,522,503
Repurchage agreement, Weighted Average Interest Rate	0.39%	0.42%
Fair Value of Collateral Pledged	2,064,704	2,598,158
Residential Mortgage Backed Securities [Member] \| Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	17,594	10,569
Repurchage agreement, Weighted Average Interest Rate	1.57%	1.80%
Fair Value of Collateral Pledged	21,787	12,746
Commercial Mortgage Backed Securities [Member] \| Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	253,857	246,849
Repurchage agreement, Weighted Average Interest Rate	0.36%	0.39%
Fair Value of Collateral Pledged	291,103	306,318
Commercial Mortgage Backed Securities [Member] \| Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	114,895	303,674
Repurchage agreement, Weighted Average Interest Rate	1.15%	1.27%
Fair Value of Collateral Pledged	140,216	367,859
CMBS IO [Member] \| Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	372,609	369,948
Repurchage agreement, Weighted Average Interest Rate	0.92%	1.16%
Fair Value of Collateral Pledged	430,638	449,072
CMBS IO [Member] \| Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	266,983	106,803
Repurchage agreement, Weighted Average Interest Rate	1.04%	1.27%
Fair Value of Collateral Pledged	$ 315,149	$ 136,227

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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))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Net amount of long-term deferred finance costs capitalized at the end of the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

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Weighted average maturity (weighted by amount of the agreement) of repurchase agreements with the counterparty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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)(B)(iii))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Carrying amount of financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

+ 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)

-URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729

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Carrying amount of liabilities associated with financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

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