Stock-Based Compensation (Details 2) (USD $)	12 Months Ended
Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Stock Option transactions under various stock-based employee compensation plans
Outstanding, Beginning Balance, Shares	2,828,770
Outstanding, Beginning Balance, Weighted Average Exercise Price	$ 20.85
Granted, shares	68,000
Granted, Weighted Average Exercise Price	$ 33.28
Exercised, Shares	(113,359)	(368,178)	(111,843)
Exercised, Weighted Average Exercise Price	$ 17.62
Cancelled, shares	(80,782)
Cancelled, Weighted Average Exercise Price	$ 21.62
Outstanding, Ending Balance, Shares	2,702,629	2,828,770
Outstanding, Ending Balance, Weighted Average Exercise Price	$ 21.27	$ 20.85
Outstanding, Ending Balance, Weighted Average Contractual Life	7.07
Exercisable, Ending Balance, Shares	1,500,656
Exercisable Ending Balance, Weighted Average Contractual Life	$ 22.86
Exercisable, Ending Balance, Weighted Average Contractual Life	6.78

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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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The weighted average period between the balance sheet date and expiration for all vested portions of options outstanding and currently exercisable (or convertible) under the plan, which may be expressed in a decimal value for number of years.

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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 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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