Derivative Instruments And Hedging Activities (Summary Of Balance Sheet Locations And Related Fair Values Of Outstanding Derivative Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Jun. 30, 2020
Derivative [Line Items]
Derivative Asset Fair Value Net Asset	$ 17,588	$ 15,141
Derivative Liability Fair Value Net Liability	14,215	13,538
Accrued Liabilities [Member]
Derivative [Line Items]
Derivative Liability Fair Value Net Liability	12,985	13,143
Prepayments And Other [Member]
Derivative [Line Items]
Derivative Asset Fair Value Net Asset	17,588	15,141
Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liability Fair Value Net Liability	1,230	395
Forward Contracts [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		0
Derivative Asset Fair Value Gross Liability		0
Derivative Asset Fair Value Net Asset		0
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7,526	1,800
Derivative Asset Fair Value Gross Liability	(1,784)	(1,194)
Derivative Asset Fair Value Net Asset	5,742	606
Derivative Liability Fair Value Gross Liability	1,230	2,529
Derivative Liability Fair Value Gross Asset	0	0
Derivative Liability Fair Value Net Liability	1,230	2,529
Designated as Hedging Instrument [Member] \| Forward Contracts [Member]
Derivative [Line Items]
Derivative Liability Fair Value Gross Liability		2,134
Derivative Liability Fair Value Gross Asset		0
Derivative Liability Fair Value Net Liability		2,134
Designated as Hedging Instrument [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7,526	1,800
Derivative Asset Fair Value Gross Liability	(1,784)	(1,194)
Derivative Asset Fair Value Net Asset	5,742	606
Derivative Liability Fair Value Gross Liability	1,230	395
Derivative Liability Fair Value Gross Asset	0	0
Derivative Liability Fair Value Net Liability	1,230	395
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	11,846	16,939
Derivative Asset Fair Value Gross Liability	0	(2,404)
Derivative Asset Fair Value Net Asset	11,846	14,535
Derivative Liability Fair Value Gross Liability	12,985	11,009
Derivative Instruments Not Designated as Hedging Instruments, Loss	0
Derivative Liability Fair Value Gross Asset	0	0
Derivative Liability Fair Value Net Liability	12,985	11,009
Not Designated as Hedging Instrument [Member] \| Nymex Futures Contracts [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Asset Fair Value Gross Liability	0	0
Derivative Asset Fair Value Net Asset	0	0
Derivative Liability Fair Value Gross Liability	2,578	6,987
Derivative Liability Fair Value Gross Asset		0
Derivative Liability Fair Value Net Liability	2,578	6,987
Not Designated as Hedging Instrument [Member] \| NYMEX WTI Short [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7,713	2,955
Derivative Asset Fair Value Gross Liability	0	0
Derivative Asset Fair Value Net Asset	7,713	2,955
Derivative Liability Fair Value Gross Liability	0	0
Derivative Liability Fair Value Gross Asset		0
Derivative Liability Fair Value Net Liability	0	0
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	4,133	4,219
Derivative Asset Fair Value Gross Liability	0	0
Derivative Asset Fair Value Net Asset	4,133	4,219
Derivative Liability Fair Value Gross Liability	3,685	4,022
Derivative Liability Fair Value Gross Asset	0	0
Derivative Liability Fair Value Net Liability	3,685	4,022
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	9,765
Derivative Asset Fair Value Gross Liability		(2,404)
Derivative Asset Fair Value Net Asset	0	7,361
Derivative Liability Fair Value Gross Liability	6,722	0
Derivative Liability Fair Value Gross Asset		0
Derivative Liability Fair Value Net Liability	$ 6,722	$ 0

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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Aggregate fair value of all derivative assets designated as hedging instruments. Includes instruments designated as cash flow hedges, fair value hedges, and hedges of net investments in foreign operations.

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Amount of realized and unrealized loss of derivative instruments not designated or qualifying as hedging instruments.

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