Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	$ 628,494
Less: current portion	(23,353)	$ (116,164)
Long-Term Debt
Long-term debt	605,141	$ 335,790
US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	450,457
Less: current portion	(457)
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	178,037
Less: current portion	(22,896)
Long-Term Debt
Long-term debt	155,141
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	139,665
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	139,665
Credit facility [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	115,476
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	15,476
Other local arrangements [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	23,353
Other local arrangements [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	457
Other local arrangements [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	$ 22,896