Earnings per Share - Reconciliation of Basic Earnings Per Share to Diluted Earnings Per Share for Income from Continuing Operations (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Income from continuing operations	$ 99	$ 136
Weighted average common shares for basic earnings per share	170	190
Effect of dilutive stock options and restricted stock awards	1	2
Weighted average common shares for diluted earnings per share	171	192
Basic earnings per share	$ 0.59	$ 0.71
Diluted earnings per share	$ 0.58	$ 0.71

Earnings per Share - Reconciliation of Basic Earnings Per Share to Diluted Earnings Per Share for Income from Continuing Operations (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified

3 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Earnings Per Share [Abstract]

Income from continuing operations

$ 99us-gaap_IncomeLossFromContinuingOperations

$ 136us-gaap_IncomeLossFromContinuingOperations

Weighted average common shares for basic earnings per share

170us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

190us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

Effect of dilutive stock options and restricted stock awards

1us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

2us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

Weighted average common shares for diluted earnings per share

171us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

192us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

Basic earnings per share

$ 0.59us-gaap_IncomeLossFromContinuingOperationsPerBasicShare

$ 0.71us-gaap_IncomeLossFromContinuingOperationsPerBasicShare

Diluted earnings per share

$ 0.58us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare

$ 0.71us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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