Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	$ 793	$ 2,517
Liability derivatives	(1,310)	(348)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	0	0
Liability derivatives	0	0
Bank acceptances	0	0
Rabbi trust assets	2,704	2,457
Financial assets and financial liabilities, reported at fair value	2,704	2,457
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	793	2,517
Liability derivatives	(1,310)	(348)
Bank acceptances	10,212	17,698
Rabbi trust assets	0	0
Financial assets and financial liabilities, reported at fair value	9,695	19,867
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	0	0
Liability derivatives	0	0
Bank acceptances	0	0
Rabbi trust assets	0	0
Financial assets and financial liabilities, reported at fair value	0	0
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset derivatives	793	2,517
Liability derivatives	(1,310)	(348)
Bank acceptances	10,212	17,698
Rabbi trust assets	2,704	2,457
Financial assets and financial liabilities, reported at fair value	$ 12,399	$ 22,324
Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity of bank acceptances	3 months
Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity of bank acceptances	6 months