Securities - Other than Temporary Impairment, Credit Losses Recognized in Earnings (Details) (Held-to-maturity Securities [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Held-to-maturity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance of credit losses on held-to-maturity debt securities for which a portion of an other-than-temporary impairment was recognized in other comprehensive income (loss)	$ 0	$ 61
Increase in credit losses for which an other-than-temporary impairment was previously recognized	0	2
Ending balance of credit losses on held-to-maturity debt securities for which a portion of an other-than-temporary impairment was recognized in other comprehensive income (loss)	$ 0	$ 63

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563

Name:	us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration