Derivative Instruments and Hedging Activities (Details) In Thousands, unless otherwise specified			3 Months Ended		6 Months Ended
	Jun. 30, 2014 item	Dec. 31, 2013 item	Jun. 30, 2014 Foreign exchange contracts USD ($)	Jun. 30, 2013 Foreign exchange contracts USD ($)	Jun. 30, 2014 Foreign exchange contracts USD ($)	Jun. 30, 2013 Foreign exchange contracts USD ($)	Jun. 30, 2014 Forward contracts Purchases U.S. dollars: British pounds sterling USD ($)	Jun. 30, 2014 Forward contracts Purchases U.S. dollars: Australian dollars USD ($)	Jun. 30, 2014 Forward contracts Purchases Euros : U.S. dollars EUR (€)	Jun. 30, 2014 Forward contracts Sales U.S. dollars: British pounds sterling GBP (£)	Jun. 30, 2014 Forward contracts Sales U.S. dollars: Australian dollars AUD	Jun. 30, 2014 Forward contracts Sales Euros : U.S. dollars USD ($)
Derivative Instruments and Hedging Activities
Targeted percentage of debt portfolio to be fixed with interest rates	75.00%
Number of derivative instrument with contingent features of credit risk	0	0
Derivative instruments
Notional amount of derivatives							$ 311,944	$ 61,849	€ 142,500	£ 186,000	66,000	$ 195,157
Net cash receipts from foreign currency forward contracts				10,476		16,275
Net cash payments from foreign currency forward contracts			$ 7,330		$ 14,529