Other Income (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Component of Other Income (Expense), Nonoperating [Line Items]
Other income	$ 3,362	$ 2,880	$ 2,351
Gain (loss) on currency transactions
Component of Other Income (Expense), Nonoperating [Line Items]
Other income	775	2,641	1,905
Hedge ineffectiveness
Component of Other Income (Expense), Nonoperating [Line Items]
Other income	1,860	218	(1,247)
Other non-operating income
Component of Other Income (Expense), Nonoperating [Line Items]
Other income	$ 727	$ 21	$ 1,693