Foreign Currency Derivative Instruments (Gains and losses on foreign currency derivative contracts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Foreign Currency Derivatives [Abstract]
Net gains (loss) on foreign currency forward contracts were partially offset on assets and liabilities	$ (984)	$ (207)	$ (754)
Cost of revenue [Member]
Foreign Currency Derivatives [Abstract]
Net gains (loss) on foreign currency forward contracts were partially offset on assets and liabilities	13	108	717
Selling, general and administrative [Member]
Foreign Currency Derivatives [Abstract]
Net gains (loss) on foreign currency forward contracts were partially offset on assets and liabilities	$ (997)	$ (315)	$ (1,471)