Earnings Per Share - Reconciliation of the Earnings (Losses) and Number of Shares Used in Calculations of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Computation of Basic Earnings Per Share
Net income	$ 207us-gaap_NetIncomeLoss	$ 172us-gaap_NetIncomeLoss
Weighted average shares outstanding	277.7	296.1
Basic earnings per share (in USD per share)	$ 0.75us-gaap_EarningsPerShareBasic	$ 0.58us-gaap_EarningsPerShareBasic
Computation of Diluted Earnings Per Share
Net income	$ 207us-gaap_NetIncomeLoss	$ 172us-gaap_NetIncomeLoss
Weighted average shares outstanding	277.7	296.1
Effect of dilutive securities
Shares for diluted earnings per share	283.5	303.3
Diluted earnings per share (in USD per share)	$ 0.73us-gaap_EarningsPerShareDiluted	$ 0.57us-gaap_EarningsPerShareDiluted
Employee stock option and appreciation right plans
Effect of dilutive securities
Effect of dilutive securities	2.4	3.4
Deferred stock incentive plans
Effect of dilutive securities
Effect of dilutive securities	0.7	0.8
Restricted stock units
Effect of dilutive securities
Effect of dilutive securities	2.7	3.0

Earnings Per Share - Reconciliation of the Earnings (Losses) and Number of Shares Used in Calculations of Basic and Diluted Earnings Per Share (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified

3 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Computation of Basic Earnings Per Share

Net income

$ 207us-gaap_NetIncomeLoss

$ 172us-gaap_NetIncomeLoss

Weighted average shares outstanding

277.7us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

296.1us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

Basic earnings per share (in USD per share)

$ 0.75us-gaap_EarningsPerShareBasic

$ 0.58us-gaap_EarningsPerShareBasic

Computation of Diluted Earnings Per Share

Net income

$ 207us-gaap_NetIncomeLoss

$ 172us-gaap_NetIncomeLoss

Weighted average shares outstanding

277.7us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

296.1us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

Effect of dilutive securities

Shares for diluted earnings per share

283.5us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

303.3us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

Diluted earnings per share (in USD per share)

$ 0.73us-gaap_EarningsPerShareDiluted

$ 0.57us-gaap_EarningsPerShareDiluted

Employee stock option and appreciation right plans

Effect of dilutive securities

Effect of dilutive securities

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Deferred stock incentive plans

Effect of dilutive securities

Effect of dilutive securities

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Effect of dilutive securities

Effect of dilutive securities

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- Definition

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

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The amount of net income (loss) for 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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