Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Notional amounts of foreign currency forward contracts	$ 119,008	$ 121,930
Swedish Kronor
Notional amounts of foreign currency forward contracts	67,809	99,214
Canadian Dollar
Notional amounts of foreign currency forward contracts	17,446	2,914
British Pound Sterling
Notional amounts of foreign currency forward contracts	14,928	5,641
Australian Dollar
Notional amounts of foreign currency forward contracts	6,566	5,986
Euro
Notional amounts of foreign currency forward contracts	5,391	265
Japanese Yen
Notional amounts of foreign currency forward contracts	3,718	4,462
Other
Notional amounts of foreign currency forward contracts	$ 3,150	$ 3,448