Financial Instruments Measured at Fair Value - Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	$ 16,279		$ 289,938
Equity investments	50,079		52,683
Interest rate swaps- liability	(645)		(149)
Foreign exchange contracts - asset	7,641		5,499
Foreign exchange contracts - liability	(3,276)		(8,581)
Contingent consideration	(3,214)		(3,176)
Total Fair Value Assets And Liabilities Measured On Recurring Basis	66,864		336,214
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	16,279	[1]	3,267
Equity investments	50,079		52,683	[2]
Interest rate swaps- liability	0		0
Foreign exchange contracts - asset	0		0
Foreign exchange contracts - liability	0		0
Contingent consideration	0		0
Total Fair Value Assets And Liabilities Measured On Recurring Basis	66,358		55,950
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	0		286,671	[3]
Equity investments	0		0
Interest rate swaps- liability	(645)		(149)
Foreign exchange contracts - asset	7,641		5,499
Foreign exchange contracts - liability	(3,276)		(8,581)
Contingent consideration	0		0
Total Fair Value Assets And Liabilities Measured On Recurring Basis	3,720		283,440
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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
Contingent consideration	(3,214)		(3,176)
Total Fair Value Assets And Liabilities Measured On Recurring Basis	$ (3,214)		$ (3,176)

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

[2] (b)The company has an 8.4% equity ownership interest in Marubun Corporation and a portfolio of mutual funds with quoted market prices.

[3] (c)Cash equivalents at December 31, 2017 included $286,671 invested in certificates of deposit, with an original maturity of less than three months, held in anticipation of our acquisition of eInfochips, which closed in January 2018 (see Note D).