Long-Term Debt Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total long-term debt	$ 1,705,210	$ 1,837,372
Current portion of long-term debt	307,294	422,012
Long-term debt	1,397,916	1,415,360
Senior Notes | 1.875% Senior Notes
Debt Instrument [Line Items]
Total long-term debt	444,155	463,575
Senior Notes | 4.15% Senior Notes
Debt Instrument [Line Items]
Total long-term debt	422,116	421,628
Senior Notes | 4.50% Senior Notes
Debt Instrument [Line Items]
Total long-term debt	174,626	174,325
Senior Notes | 5.45% Senior Notes
Debt Instrument [Line Items]
Total long-term debt	345,996	345,841
Commercial Paper
Debt Instrument [Line Items]
Total long-term debt	306,606	421,321
Variable-rate foreign bank loans
Debt Instrument [Line Items]
Total long-term debt	7,216	5,298
Other long-term debt
Debt Instrument [Line Items]
Total long-term debt	$ 4,495	$ 5,384