Derivative Instruments and Hedging Activities (Summary Of Balance Sheet Locations And Related Fair Values Of Outstanding Derivative Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	$ (40,280)	$ (3,840)
Derivative Liability, Fair Value, Net Liability	2,093	6,804
Prepayments and other
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	(37,982)	(3,840)
Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Net Liability	1,137	5,365
Other Intangible Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	(2,298)
Other Long Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Net Liability	956	1,439
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	11,790	3,067
Derivative Asset, Fair Value, Gross Liability	973	0
Derivative, Fair Value, Net	(10,817)	(3,067)
Derivative Liability, Fair Value, Gross Liability	1,755	2,842
Derivative Liability, Fair Value, Gross Asset	(799)	0
Derivative Liability, Fair Value, Net Liability	956	2,842
Designated as Hedging Instrument [Member] \| Commodity price swaps
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	11,790
Derivative Asset, Fair Value, Gross Liability	(973)
Derivative, Fair Value, Net	(10,817)
Derivative Liability, Fair Value, Gross Liability	1,755	2,424
Derivative Liability, Fair Value, Gross Asset	(799)	0
Derivative Liability, Fair Value, Net Liability	956	2,424
Designated as Hedging Instrument [Member] \| Commodity forward contracts
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		3,067
Derivative Asset, Fair Value, Gross Liability		0
Derivative, Fair Value, Net		(3,067)
Derivative Liability, Fair Value, Gross Liability		418
Derivative Liability, Fair Value, Gross Asset		0
Derivative Liability, Fair Value, Net Liability		418
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	29,463	773
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative, Fair Value, Net	(29,463)	(773)
Derivative Liability, Fair Value, Gross Liability	1,137	3,962
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Net Liability	1,137	3,962
Not Designated as Hedging Instrument [Member] \| Commodity forward contracts
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,034	773
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative, Fair Value, Net	(1,034)	(773)
Derivative Liability, Fair Value, Gross Liability	1,137	602
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Net Liability	1,137	602
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	25,956
Derivative Asset, Fair Value, Gross Liability	0
Derivative, Fair Value, Net	(25,956)
Not Designated as Hedging Instrument [Member] \| Nymex Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,473	0
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative, Fair Value, Net	2,473	0
Derivative Liability, Fair Value, Gross Liability	0	3,360
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Net Liability	$ 0	$ 3,360

Fair value of liability associated with 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.

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