Share-based Compensation (Details 5) (Stock options, USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Stock options
Share-Based Compensation
Exercise Price Range, Lower Range Limit (in dollars per share)	$ 1.84
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 32.69
Option grants outstanding, weighted average remaining contractual life	6 years 10 months 20 days
Number of options, outstanding (in shares)	9,687,716	8,814,831
Number of options, exercisable (in shares)	5,298,336
Weighted average exercise price, Outstanding (in dollars per share)	$ 16.20	$ 15.26
Weighted average exercise price, Exercisable (in dollars per share)	$ 12.92
Weighted average remaining contractual term, Outstanding	6 years 10 months 20 days
Weighted average remaining contractual term, Exercisable	5 years 4 months 28 days
Aggregate intrinsic value, Outstanding	$ 90,276
Aggregate intrinsic value, Exercisable	$ 66,118

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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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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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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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

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