Mortgage Securities And Similar Investments (Narrative) (Details) (USD $)	9 Months Ended
Sep. 30, 2011	Dec. 31, 2009
Schedule of Mortgage Securities and Similar Investments [Line Items]
Mortgage securities weighted average contractual maturity, months	290
Number of unsold completed units	13
Amount of securities collateralized	$ 3,100,000
Impairment charge related to real estate held for sale	470,000
Amount of investment written off		39,200,000
Maximum [Member]
Schedule of Mortgage Securities and Similar Investments [Line Items]
Agency securities months to roll	18
Minimum [Member]
Schedule of Mortgage Securities and Similar Investments [Line Items]
Agency securities months to roll	18
Current-Reset ARMs [Member]
Schedule of Mortgage Securities and Similar Investments [Line Items]
Investments held, basis amount	8,730,000,000
Agency securities average months to roll	5.8
Longer-To-Reset ARMs [Member]
Schedule of Mortgage Securities and Similar Investments [Line Items]
Investments held, basis amount	$ 3,260,000,000
Agency securities average months to roll	46.3

The average number of months until coupon reset. Current reset ARM securities have a months to roll of less than 18 months, while longer-to-reset ARM securities have a months to roll of 18 months or greater.

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- Definition

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Represents the weighted average contractual maturity period of the portfolio without giving affect to mortgage prepayments.

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Schedule Of Mortgage Securities And Similar Investments [Line Items]

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- Definition

The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6390789&loc=d3e2420-110228

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 45, 46, 47

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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Cost of the investment.

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- Definition

The number of units in a real estate property owned as of the balance sheet date.

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The carrying amount, as of the date of the latest financial statement presented, of real estate owned but transferred to serve as collateral for the payment of the related debt obligation, primarily a secured borrowing or repurchase agreement, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ 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)

-URI http://asc.fasb.org/extlink&oid=6862952&loc=SL6224234-111729

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-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS140-4/FIN46(R)-8

-Paragraph B6

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 17

-Subparagraph a(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The amount of any write-down or reserve provided in the period on a real estate investment.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 970

-SubTopic 360

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-28.FN5)

-URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule III

-Article 5

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 28

-Article 12

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

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-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule III)

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