Foreign Currency Derivative Instruments (Gains and losses on foreign currency forward contracts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Foreign Currency Derivatives [Abstract]
Total gain (loss)	$ (5,265)	$ 359	$ 393
Cost of revenue [Member]
Foreign Currency Derivatives [Abstract]
Total gain (loss)	9	27	(2)
Selling, general and administrative [Member]
Foreign Currency Derivatives [Abstract]
Total gain (loss)	$ (5,274)	$ 332	$ 395