Share-Based Compensation (Details) (USD $)	6 Months Ended
Jun. 30, 2011
Summary of stock option activity
Stock Options, Beginning balance	3,323,000
Stock Options, Exercised	(242,000)
Stock option, Canceled	(3,000)
Stock Options, Ending balance	3,078,000
Stock Options, Exercisable	2,739,000
Stock Options, Vested and Expected to Vest	3,063,000
Weighted-Average Exercise Price, Beginning balance	$ 16.45
Weighted-Average Exercise Price, Exercised	$ 10.14
Weighted-Average Exercise Price, Canceled	$ 17.04
Weighted-Average Exercise Price, Ending balance	$ 16.94
Weighted-Average Exercise Price, Exercisable	$ 16.93
Weighted-Average Exercise Price, Vested and Expected to Vest	$ 16.94
Summary of nonvested stock activity
Shares, Beginning balance	686,511
Shares, Granted	1,148,046
Shares, Vested	(268,215)
Shares, Forfeited/Canceled	(1,896)
Shares, Ending balance	1,564,446
Grant Date Weighted-Average Fair Value Per Share, Beginning balance	$ 26.16
Grant Date Weighted-Average Fair Value Per Share, Granted	$ 20.27
Grant Date Weighted-Average Fair Value Per Share, Vested	$ 30.83
Grant Date Weighted-Average Fair Value Per Share, Forfeited/Canceled	$ 30.35
Grant Date Weighted-Average Fair Value Per Share, Ending balance	$ 21.03

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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

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

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