Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	$ 156,858	$ 152,984
Swedish Kronor
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	15,247	59,373
Canadian Dollar
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	10,829	7,426
Brazil, Brazil Real
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	7,800	7,794
Australian Dollar
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	1,395	2,817
United Kingdom, Pounds
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	4,542	34,317
Euro
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	107,746	34,800
Japanese Yen
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	1,708	3,362
Norway, Krone
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	$ 7,591	$ 3,095