Schedule Of Information About All Outstanding Options And Exercisable Options (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding By Exercise Price [Line Items]
Number, Options Outstanding	7,436,238	7,558,945	6,594,950	8,802,450
Weighted average exercise price, Options Outstanding	$ 36.31	$ 31.63	$ 25.16	$ 25.03
Aggregate intrinsic value, Options Outstanding	$ 89,595,385
Weighted average remaining contractual life, Options Outstanding	3 years
Number, Options Exercisable	2,185,312
Weighted Average Exercise Price, Options Exercisable	$ 30.40
Aggregate intrinsic value, Options Exercisable	$ 39,256,370
Weighted average remaining contractual life, Options Exercisable	2 years

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

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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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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 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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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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