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Share-based compensation plans - Options Activity (Detais) (USD $)
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3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
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Sep. 30, 2011
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| Share-based Compensation Plans Optoins Outstanding Exercise Price [Abstract] | ||||
| Options granted - Exercise Price | $ 22.56 | $ 31.47 | $ 22.47 | $ 31.47 |