Derivative instruments used in hedging activities (Details) (Designated as Hedging Instrument [Member], Foreign exchange contract [Member], USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Summary of amount of derivatives designated as hedging instruments
Notional amount	$ 128,613	$ 75,000
Other assets [Member]
Summary of amount of derivatives designated as hedging instruments
Fair value, derivative assets	354	2,905
Other liabilities [Member]
Summary of amount of derivatives designated as hedging instruments
Fair value, derivative liabilities	$ 173	$ 0