Share-based Compensation-Options roll forward (Details) (Employee Stock Option [Member], USD $)	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options Outstanding, beginning of the year (shares)	1,201,000	1,277,200
Options Outstanding, granted (shares)	246,000	361,331
Options Outstanding, Exercised (shares)	(184,919)	(382,612)
Options Outstanding, Lapsed or canceled (shares)	(33,202)	(54,919)
Options Outstanding, end of the year (shares)	1,228,879	1,201,000
Options Outstanding, options exercisable at the end of the period (shares)	506,903	479,913
Options Outstanding, weighted average fair value of options granted during the period	$ 4,999,225	$ 6,602,967
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, beginning of the year (usd per share)	$ 75.05	$ 63.37
Weighted Average Exercise Price, granted (usd per share)	$ 79.58	$ 75.36
Weighted Average Exercise Price, exercised (usd per share)	$ 51.62	$ 36.65
Weighted Average Exercise Price, lapsed or canceled (usd per share)	$ 83.61	$ 72.99
Weighted Average Exercise Price, end of the year (usd per share)	$ 79.25	$ 75.05
Weighted Average Exercise Price, options exercisable at the end of the period (usd per share)	$ 87.48	$ 86.85

Represents the weighted average fair value of awards granted during the period.

No definition available.

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- Definition

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.

+ References

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- Definition

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

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- Definition

For presentations that combine terminations, 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 or that expired.

+ References

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- Definition

Weighted average price of options that were either forfeited or expired.

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- Definition

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

+ References

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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

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