Other-Than-Temporary Impairment Losses (Significant Assumptions Used In The Valuation Of Non-Agency Mortgage-Backed Securities) (Details)	3 Months Ended
Jun. 30, 2012
Weighted Average [Member]
Schedule of Available-for-sale Securities [Line Items]
Prepayment rates	13.80%
Default rates	11.30%
Loss severity	46.70%
Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Prepayment rates	5.10%
Default rates	5.40%
Loss severity	36.40%
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Prepayment rates	20.10%
Default rates	19.90%
Loss severity	61.80%

This item represents the default rate of the underlying assets in the security that were considered as one of the potential factors in reaching a conclusion that the available-for-sale investments are not other-than-temporarily impaired.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 17

-Subparagraph b

-Clause 5

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration