Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total long-term Debt	$ 1,921,944	$ 1,705,210
Current portion of long-term debt	539,960	307,294
Long-term debt	1,381,984	1,397,916
Senior Notes | 1.875% Senior Notes
Debt Instrument [Line Items]
Total long-term Debt	427,941	444,155
Senior Notes | 4.15% Senior Notes
Debt Instrument [Line Items]
Total long-term Debt	422,481	422,116
Senior Notes | 4.50% Senior Notes
Debt Instrument [Line Items]
Total long-term Debt	174,852	174,626
Senior Notes | 5.45% Senior Notes
Debt Instrument [Line Items]
Total long-term Debt	346,112	345,996
Commercial paper notes
Debt Instrument [Line Items]
Total long-term Debt	539,300	306,606
Variable-rate foreign bank loans
Debt Instrument [Line Items]
Total long-term Debt	7,424	7,216
Finance lease obligations
Debt Instrument [Line Items]
Total long-term Debt	$ 3,834	$ 4,495