Stock Option Activity (Detail) (USD $)	12 Months Ended
Dec. 31, 2011
Shares
Outstanding at beginning of year	7,710,102
Granted	419,500
Exercised	(1,048,307)
Cancelled
Expired
Outstanding at end of year	7,081,295
Exercisable at end of year	6,077,635
Weighted Average Exercise Price
Outstanding at beginning of year	$ 19.58
Granted	$ 30.28
Exercised	$ 16.04
Cancelled
Expired
Outstanding at end of year	$ 20.73
Exercisable at end of year	$ 20.69

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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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The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

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The decrease in the number of shares that could be issued attributable to the lapse of rights to exercise previously issued stock options under the terms of the option agreements under the plan during the reporting period.

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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that lapsed during the reporting period.

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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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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated during the reporting period due to noncompliance with plan terms during the reporting period.

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

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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 stock options awarded under the plan during the reporting period.

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The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

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

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