Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	$ 622,792
Less: current portion	(21,061)	$ (116,164)
Long-Term Debt
Long-term debt	601,731	$ 335,790
US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	450,283
Less: current portion	(283)
Long-Term Debt
Long-term debt	450,000
Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	172,509
Less: current portion	(20,778)
Long-Term Debt
Long-term debt	151,731
3.67% Senior Notes [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	50,000
3.67% Senior Notes [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	50,000
3.67% Senior Notes [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
4.10% Senior Notes [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	50,000
4.10% Senior Notes [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	50,000
4.10% Senior Notes [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
3.84% Senior Notes [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	125,000
3.84% Senior Notes [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	125,000
3.84% Senior Notes [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
4.24% Senior Notes [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	125,000
4.24% Senior Notes [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	125,000
4.24% Senior Notes [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
1.47% EURO Senior Notes [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	139,962
1.47% EURO Senior Notes [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
1.47% EURO Senior Notes [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	139,962
Credit facility [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	111,769
Credit facility [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	100,000
Credit facility [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	11,769
Other local arrangements [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	21,061
Other local arrangements [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	283
Other local arrangements [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	$ 20,778