Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Condensed Consolidated Statements of Comprehensive Income [Abstract]
Tax effects on unrealized gains (losses) resulting from changes in fair value	$ 2	$ (3)
Tax effects on realized (gains) losses on derivative instruments reclassified into earnings	2	5
Tax effects on unrealized gains (losses) on available-for-sale securities	1	(1)
Tax effects on change in funded status of post-retirement benefit obligations	$ 0	$ (1)

Tax effect on the accumulated change in the value of either the projected benefit obligation or the plans assets resulting from experience different from that assumed or from a change in an actuarial assumption that has not been recognized in net periodic benefit cost pursuant to FAS 87 and 106.

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph c(3)

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 25

+ Details

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

- Definition

Tax effect on reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period.

+ References

+ Details

Name:	us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentOnDerivativesIncludedInNetIncomeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Tax effect on the change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses.

+ References

+ Details

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

- Definition

Tax effect on gross appreciation or the gross loss in value of the total of unsold securities during the period being reported on.

+ References

+ Details

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

- Details

Name:	us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration