Derivatives (Fair Values Of Derivative Contracts) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gross fair value of assets	$ 25,832	$ 30,422
Gross liabilities offset against assets in the Balance Sheet	(18,597)	(11,052)
Net fair value of assets presented in the Balance Sheet	7,235	19,370
Gross fair value of liabilities	19,626	12,942
Gross assets offset against liabilities in the Balance Sheet	(18,597)	(11,052)
Net fair value of liabilities presented in the Balance Sheet	1,029	1,890
Derivatives, current assets
Derivatives, Fair Value [Line Items]
Gross fair value of assets	13,855	22,512
Gross liabilities offset against assets in the Balance Sheet	(9,128)	(6,089)
Net fair value of assets presented in the Balance Sheet	4,727	16,423
Derivatives, long-term assets
Derivatives, Fair Value [Line Items]
Gross fair value of assets	11,977	7,910
Gross liabilities offset against assets in the Balance Sheet	(9,469)	(4,963)
Net fair value of assets presented in the Balance Sheet	2,508	2,947
Derivatives, current liabilities
Derivatives, Fair Value [Line Items]
Gross fair value of liabilities	9,968	7,799
Gross assets offset against liabilities in the Balance Sheet	(9,128)	(6,089)
Net fair value of liabilities presented in the Balance Sheet	840	1,710
Derivatives, long-term liabilities
Derivatives, Fair Value [Line Items]
Gross fair value of liabilities	9,658	5,143
Gross assets offset against liabilities in the Balance Sheet	(9,469)	(4,963)
Net fair value of liabilities presented in the Balance Sheet	$ 189	$ 180

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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Fair value, after offset of derivative liability, of 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, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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