Financial Instruments and Risk Management (Fair Value of Derivative Instruments Not Designated as Hedging Instruments) (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Commodity Derivative Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives		$ 89,400,000
Foreign Exchange Derivative Contracts [Member] | Accounts Payable [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 73,000	29,000
Nondesignated [Member] | Commodity Derivative Contracts [Member] | Accounts Receivable [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives		89,358,000
Nondesignated [Member] | Commodity Derivative Contracts [Member] | Accounts Payable [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	48,864,000
Nondesignated [Member] | Foreign Exchange Derivative Contracts [Member] | Accounts Payable [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ 73,000	$ 29,000