Stock-Based Compensation (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2012
Summary of information concerning stock options
Stock Options Vested or Expected to Vest, Stock options	496,967
Stock options, Exercisable	229,136
Stock Options Vested or Expected to Vest, Weighted average remaining contractual life in years	6 years 7 months 21 days
Weighted average remaining contractual life in years, Exercisable	4 years
Stock Options Vested or Expected to Vest, Weighted average exercise price on shares above water	$ 13.22
Weighted average exercise price on shares above water, Exercisable	$ 12.17
Stock Options Vested or Expected to Vest, Aggregate intrinsic value	$ 294,614
Aggregate intrinsic value, Exercisable	$ 66,268

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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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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

+ References

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options that are 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 prices of fully vested and expected to vest options outstanding.

+ References

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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

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