Derivative Instruments (Fair Values of Derivative Instruments in Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accrued liabilities
Derivatives, Fair Value [Line Items]
Total derivative liabilities	$ 15,267	$ 10,108
Accounts receivable, net
Derivatives, Fair Value [Line Items]
Total derivative assets	4,739	3,145
Forward Contracts [Member] | Accrued liabilities
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	5,421	6,549
Forward Contracts [Member] | Accounts receivable, net
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	2,722	3,145
Forward Contracts [Member] | Deferred charges and other assets, net
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	2,017	0
Commodity Forward Contracts [Member] | Other liabilities
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	$ 9,846	$ 3,559