Fair Value and Investment Securities Roll-Forward of ARS Investments (Details) (Significant Unobservable Inputs (Level 3), USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Significant Unobservable Inputs (Level 3)
Investment Identifier [Line Items]
Fair value, Beginning Balance	$ 32	$ 70
Calls, at par	(23)	(42)
Recovery of unrealized losses due to issuer calls	2	4
Fair value, Ending Balance	$ 11	$ 32

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant