Derivative Financial Instruments Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Notional amount of foreign currency derivatives	$ 122,006	$ 129,037
Swedish kronor
Notional amount of foreign currency derivatives	86,156	98,385
British pound sterling
Notional amount of foreign currency derivatives	4,793	15,619
Australian dollar
Notional amount of foreign currency derivatives	4,075	7,022
Japanese yen
Notional amount of foreign currency derivatives	4,122	5,157
Euro
Notional amount of foreign currency derivatives	17,777	2,232
Brazilian real
Notional amount of foreign currency derivatives	4,240	0
Other
Notional amount of foreign currency derivatives	$ 843	$ 622