Income Taxes - Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits, Including Accrued interest (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance beginning	$ 49us-gaap_UnrecognizedTaxBenefits	$ 54us-gaap_UnrecognizedTaxBenefits	$ 49us-gaap_UnrecognizedTaxBenefits
Additions based on tax positions related to the current year	9	6	15
Additions based on tax positions of prior years	2
Additions due to acquisitions	0	0	0
Accrued interest	1	2	2
Reductions based on tax positions related to the current year	0	0	0
Reductions for tax positions of prior years		(7)	(1)
Settlements	(11)	(1)	(4)
Lapse of statute of limitations	(8)	(5)	(7)
Balance ending	$ 42us-gaap_UnrecognizedTaxBenefits	$ 49us-gaap_UnrecognizedTaxBenefits	$ 54us-gaap_UnrecognizedTaxBenefits

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

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

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Amount of decrease 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 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 acquisitions.

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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 interest expense for an underpayment of income taxes.

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

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