Employee benefits (Details 3) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012 USD [Member] USD ($)	Dec. 31, 2011 USD [Member] USD ($)	Dec. 31, 2010 USD [Member] USD ($)	Dec. 31, 2012 Euro [Member] EUR (€)	Dec. 31, 2011 Euro [Member] EUR (€)	Dec. 31, 2010 Euro [Member] EUR (€)
Stock options
Weighted average fair value of stock options granted	$ 11.87	$ 10.42	$ 11.10	€ 8.97	€ 8.28	€ 8.22
Weighted average share price at the exercise date of stock options	$ 50.88	$ 41.94	$ 33.79	€ 40.45	€ 29.39	€ 25.77
Aggregate intrinsic value of stock options exercised	$ 12,684	$ 11,323	$ 13,669	€ 71,331	€ 30,204	€ 22,720
Aggregate remaining contractual term of currently exercisable options (years)	3 years 2 months 1 day	1 year 9 months 18 days	2 years 7 months 2 days	3 years 7 months 2 days	2 years 29 days	2 years 10 months 10 days
Aggregate intrinsic value of exercisable stock options	21,882	20,492	25,780	34,438	39,384	54,109
Aggregate intrinsic value of outstanding stock options	$ 22,433	$ 20,791	$ 28,024	€ 35,671	€ 45,141	€ 65,240

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Weighted average share price at the date of exercise for stock options.

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No definition available.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of options outstanding.

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