Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures
Equity Method Investment, Ownership Percentage		8.40%
Unrealized Gain (Loss) on Securities		$ 4,204		$ (13,854)	$ 14,596
Fair Value, Measurements, Recurring [Member]
Fair Value Disclosures
Cash and Cash Equivalents		18,579	[1]	22,883
Equity investments	[2]	44,677		38,045
Interest rate swaps - liability		(11,574)		(589)
Foreign exchange contracts - asset		24,092		4,163
Foreign exchange contracts - liability		(2,132)		(2,384)
Total Fair Value Assets And Liabilities Measured On Recurring Basis		73,642		62,118
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Disclosures
Cash and Cash Equivalents		18,579	[1]	22,883
Equity investments	[2]	44,677		38,045
Interest rate swaps - liability		0		0
Foreign exchange contracts - asset		0		0
Foreign exchange contracts - liability		0		0
Total Fair Value Assets And Liabilities Measured On Recurring Basis		63,256		60,928
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Disclosures
Cash and Cash Equivalents		0		0
Equity investments		0		0
Interest rate swaps - liability		(11,574)		(589)
Foreign exchange contracts - asset		24,092		4,163
Foreign exchange contracts - liability		(2,132)		(2,384)
Total Fair Value Assets And Liabilities Measured On Recurring Basis		10,386		1,190
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Disclosures
Cash and Cash Equivalents		0		0
Equity investments		0		0
Interest rate swaps - liability		0		0
Foreign exchange contracts - asset		0		0
Foreign exchange contracts - liability		0		0
Total Fair Value Assets And Liabilities Measured On Recurring Basis		$ 0		$ 0

[1] Cash equivalents include highly liquid investments with an original maturity of less than three months.

[2] The company has an 8.4% equity ownership interest in Marubun Corporation and a portfolio of mutual funds with quoted market prices. During 2019, 2018, and 2017 the company recorded unrealized gains (losses) of $4,204, $(13,854), and $14,596, respectively, on equity securities held at the end of each year.