Income Taxes Reconciliaton of Changes in Unrecognized Tax Benefits Liabilities / (Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 56us-gaap_UnrecognizedTaxBenefits	$ 48us-gaap_UnrecognizedTaxBenefits	$ 110us-gaap_UnrecognizedTaxBenefits
Additions for tax positions related to current year	16	16	12
Additions for tax positions taken in prior years	13	1
Reductions for tax positions taken in prior years			(2)
Reductions for tax positions as a result of settlements	(1)		(53)
Additions for tax positions as a result of settlements		1
Reductions for tax positions as a result of lapse of statute of limitations	(6)	(10)	(19)
Ending Balance	78us-gaap_UnrecognizedTaxBenefits	56us-gaap_UnrecognizedTaxBenefits	48us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits	78us-gaap_UnrecognizedTaxBenefits	56us-gaap_UnrecognizedTaxBenefits	48us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 43

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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