Reverse Repurchase Agreements Contractual Maturities of Reverse Repurchase Agreements (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total	$ 1,100,000,000	$ 1,100,000,000
Secured Debt
Debt Instrument [Line Items]
2018	200,000,000
2019	600,000,000
2020	300,000,000
Total	1,100,000,000
Callable 2015	100,000,000
Callable 2016	100,000,000
Callable 2017	$ 100,000,000
Residential mortgage-backed securities \| Secured Debt
Debt Instrument [Line Items]
Composition of collateral that can be resold or repledged, as percentage	83.00%
Obligations of GSEs \| Secured Debt
Debt Instrument [Line Items]
Composition of collateral that can be resold or repledged, as percentage	17.00%

Composition of collateral that can be resold or repledged as a percentage to total collateral pledged.

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- Definition

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates callable in the third specified period.

+ References

No definition available.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates callable in the second specified period.

+ References

No definition available.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates callable within one year.

+ References

No definition available.

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the sixth fiscal year following the latest fiscal year.

+ References

No definition available.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

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-Topic 235

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-Section S99

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-Subparagraph (SX 210.12-04.(a))

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13(1))

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-Publisher SEC

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-Publisher FASB

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(a)(i))

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