Summary of Option Activity (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Options
Shares, Outstanding, Beginning Balance	8.9
Shares, Granted	0.3
Shares, Exercised	3.2
Shares, Forfeited
Shares, Expired
Shares, Outstanding, Ending Balance	6.0
Shares, Vested and expected to vest	5.9
Shares, Exercisable	5.0
Options
Weighted Average Exercise Price Per Share, Outstanding Beginning Balance	$ 45
Weighted Average Exercise Price Per Share, Granted	$ 79.57
Weighted Average Exercise Price Per Share, Exercised	$ 46.4
Weighted Average Exercise Price Per Share, Forfeited	$ 0
Weighted Average Exercise Price Per Share, Expired	$ 0
Weighted Average Exercise Price Per Share, Outstanding Ending Balance	$ 46
Weighted Average Exercise Price Per Share, Vested and expected to vest	$ 45.84
Weighted Average Exercise Price Per Share, Exercisable	$ 44.79
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term, Outstanding	4 years 4 months 6 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	4 years 1 month 3 days
Weighted Average Remaining Contractual Term	3 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$ 299.5
Aggregate Intrinsic Value, Vested and expected to vest	295.6
Aggregate Intrinsic Value, Exercisable	$ 252.6

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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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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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.

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

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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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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