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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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-Name Statement of Financial Accounting Standard (FAS)

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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.

+ References

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

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-Number 123R

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-Subparagraph b(1)(c)

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- Definition

The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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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.

+ References

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

-Publisher FASB

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-Number 123R

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-Subparagraph b(1)(f)

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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.

+ References

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Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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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 stock options awarded under the plan during the reporting period.

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- Definition

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

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Share Based Compensation - Option Rollforward (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Exercised	(256,000)	(315,000)	(187,000)
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price - Outstanding January 1, 2011	33.06
Weighted Average Exercise Price - Granted	33.51
Weighted Average Exercise Price - Exercised	29.63
Weighted Average Exercise Price - Forfeited	28.28
Weighted Average Exercise Price - Outstanding December 31, 2011	33.37
Exercisable at December 31, 2011	2,435,000
Weighted Average Exercise Price - Exercisable at December 31, 2011	34.85
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding January 1, 2011	3,323,000
Granted	253,000
Exercised	(256,000)
Forfeited	(9,000)
Outstanding December 31, 2011	3,311,000