Schedule of Stock Option Aggregate Intrinsic Value Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award
Exercised	$ 17,136	$ 11,307	$ 15,096
Outstanding	47,051	51,306	30,871
Vested and expected to vest	46,283	46,655	30,868
Exercisable	$ 26,436	$ 17,766	$ 21,872

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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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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

+ References

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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