Share-Based Compensation (Details) (USD $)	3 Months Ended
Mar. 31, 2012
Summary of stock option activity
Stock Options, Beginning balance	3,776,000
Stock option granted	0
Stock Options, Exercised	172,000
Stock option, Canceled	39,000
Stock Options, Ending balance	3,565,000
Stock Options, Exercisable	2,671,000
Stock Options, Vested and Expected to vest	3,525,000
Weighted-Average Exercise Price, Beginning balance	$ 16.92
Weighted-Average Exercise Price, Granted	$ 0.00
Weighted-Average Exercise Price, Exercised	$ 15.20
Weighted-Average Exercise Price, Canceled	$ 20.13
Weighted-Average Exercise Price, Ending balance	$ 16.96
Weighted-Average Exercise Price, Exercisable	$ 17.29
Weighted-Average Exercise Price, Vested and Expected to vest	$ 16.98
Summary of nonvested stock activity
Shares, Beginning balance	1,516,000
Shares, Granted	36,000
Shares, Vested	84,000
Shares, Forfeited/Canceled	(2,000)
Shares, Ending balance	1,470,000
Grant Date Weighted-Average Fair Value Per Share, Beginning balance	$ 20.76
Grant Date Weighted-Average Fair Value Per Share, Granted	$ 22.85
Grant Date Weighted-Average Fair Value Per Share, Vested	$ 30.22
Grant Date Weighted-Average Fair Value Per Share, Forfeited/Canceled	$ 25.10
Grant Date Weighted-Average Fair Value Per Share, Ending balance	$ 20.27

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

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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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Net number of share options (or share units) granted during the 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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