Stock-Based Compensation - Stock Option Activity (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Stock Options Outstanding, Beginning Balance	6.7
Stock Options, Granted	0.4
Stock Options, Exercised	(2.8)
Stock Options, Forfeited, Canceled or Expired	(0.1)
Stock Options Outstanding, Ending Balance	4.2
Stock Options, Exercisable	2.5
Stock Options Outstanding, Weighted Average Exercise Price Per Share, Beginning Balance	$ 30.70
Stock Options, Granted Weighted Average Exercise Price Per Share	$ 55.06
Stock Options, Exercised Weighted Average Exercise Price Per Share	$ 26.38
Stock Options, Forfeited, Canceled or Expired Weighted Average Exercise Price Per Share	$ 28.61
Stock Options Outstanding, Weighted Average Exercise Price Per Share, Ending Balance	$ 35.72
Stock Options, Exercisable Weighted Average Exercise Price Per Share	$ 40.06

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

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including 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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