Accumulated other comprehensive income/(loss) Schedule of accumulated other comprehensive income/(loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) , net of tax [Line Items]
Beginning balance	$ (86,381)	$ (72,289)
Other comprehensive loss before reclassifications	(10,517)	(20,221)
Amounts reclassified from AOCI	3,581	6,129
Net current period other comprehensive income/(loss)	(6,943)	(14,093)	(33,615)
Ending Balance	(93,317)	(86,381)	(72,289)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) , net of tax [Line Items]
Beginning balance	(67,135)	(52,611)
Other comprehensive loss before reclassifications	(14,204)	(14,524)
Amounts reclassified from AOCI	0	0
Net current period other comprehensive income/(loss)	(14,204)	(14,524)
Ending Balance	(81,339)	(67,135)
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss) , net of tax [Line Items]
Beginning balance	(5,976)	(6,440)
Other comprehensive loss before reclassifications	(986)	(5,665)
Amounts reclassified from AOCI	3,581	6,129
Net current period other comprehensive income/(loss)	2,595	464
Ending Balance	(3,381)	(5,976)
Pension liability
Accumulated Other Comprehensive Income (Loss) , net of tax [Line Items]
Beginning balance	(13,270)	(13,238)
Other comprehensive loss before reclassifications	4,673	(32)
Amounts reclassified from AOCI	0	0
Net current period other comprehensive income/(loss)	4,673	(32)
Ending Balance	(8,597)	(13,270)
Accumulated other comprehensive income/(loss)
Accumulated Other Comprehensive Income (Loss) , net of tax [Line Items]
Net current period other comprehensive income/(loss)	$ (6,936)	$ (14,092)	$ (33,704)