Derivative Instruments (Fair Values of Derivative Instruments in Consolidated Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accrued Liabilities
Derivatives, Fair Value [Line Items]
Total derivative liabilities	$ 6,861	$ 10,108
Accounts Receivable
Derivatives, Fair Value [Line Items]
Total derivative assets	4,484	3,145
Forward Contracts [Member] \| Accrued Liabilities
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	5,060	6,549
Forward Contracts [Member] \| Accounts Receivable
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	2,927	3,145
Forward Contracts [Member] \| Deferred charges and other assets, net
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	1,557	0
Commodity Forward Contracts [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	$ 1,801	$ 3,559

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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