Debt (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	$ 581,697
Less: current portion	(31,143)	(10,902)
Long-Term Debt
Long-term debt	550,554	670,301
6.30% Senior Notes [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	100,000
6.30% Senior Notes [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	100,000
6.30% Senior Notes [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
Credit facility [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	450,554
Credit facility [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	401,100
Credit facility [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	49,454
Other local arrangements [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	31,143
Other local arrangements [Member] | US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	0
Other local arrangements [Member] | Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	31,143
US Dollar Amounts [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	501,100
Less: current portion	0
Long-Term Debt
Long-term debt	501,100
Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Total debt	80,597
Less: current portion	(31,143)
Long-Term Debt
Long-term debt	$ 49,454