Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	$ 152,984	$ 262,065
Swedish Kronor
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	34,800	156,352
Canadian Dollar
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	7,794	2,747
British Pound Sterling
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	34,317	33,862
Brazil, Brazil Real
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	3,362	3,251
Australian Dollar
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	2,817	1,653
Euro
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	59,373	48,555
Japanese Yen
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	7,426	15,645
Other
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	$ 3,095	$ 0