Stock-Based Compensation Plans (Summary Of Stock Option Award Activity) (Detail) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 14	$ 60	$ 48
Unrecognized compensation cost	$ 8
Weighted average recognition period, in years	1 year 6 months 3 days
Number of Shares
Outstanding, beginning balance	8,724,631
Granted	1,474,177
Exercised	(637,761)
Forfeited, canceled or expired	(29,607)
Outstanding, ending balance	9,531,440	8,724,631
Vested and expected to vest at December 31, 2016 (in shares)	9,518,269
Exercisable at December 31, 2016 (in shares)	7,094,204
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 27.16
Granted (in USD per share)	35.27	$ 50.85	$ 42.51
Exercised (in USD per share)	18.78
Forfeited, canceled or expired (in USD per share)	42.91
Outstanding, ending balance (in USD per share)	28.93	$ 27.16
Vested and expected to vest at December 31, 2016 (in USD per share)	28.90
Exercisable at December 31, 2016 (in USD per share)	$ 24.90
Weighted Average Remaining Contractual Terms (in years)
Vested and expected to vest at December 31, 2016 (in years)	5 years 4 months 8 days
Exercisable at December 31, 2016 (in years)	4 years 3 months 1 day
Aggregate Intrinsic Value (in millions)
Vested and expected to vest at December 31, 2016 (in USD)	$ 205
Exercisable at December 31, 2016 (in USD)	$ 181

Share-based Compensation Arrangement by Share-based Payment Award, Options, Aggregate Intrinsic Value [Abstract]

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Abstract]

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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