Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gross Asset	$ 32,554,000	$ 46,849,000
Gross Liability	(99,429,000)	(102,453,000)
Collateral Netted	31,204,000	51,747,000
Net Asset (Liability) on Balance Sheet	(35,671,000)	(3,857,000)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	5,030,000	530,000
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	26,174,000	51,217,000
Other Current Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		0
Gross Liability		(45,000)
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		(45,000)
Other Current Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0
Gross Liability	(4,771,000)
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	(4,771,000)
Other Current Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	26,541,000	31,457,000
Gross Liability	(52,004,000)	(73,155,000)
Collateral Netted	20,960,000	37,790,000
Net Asset (Liability) on Balance Sheet	(4,503,000)	(3,908,000)
Other Current Assets [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	33,000
Gross Liability	0
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	33,000
Other Current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	771,000	5,283,000
Gross Liability	(338,000)	0
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	433,000	5,283,000
Other Current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	582,000	400,000
Gross Liability	(247,000)	(130,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	335,000	270,000
Other Property And Investments Net And Other Non-current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		5,283,000
Gross Liability		(440,000)
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		4,843,000
Other Noncurrent Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	631,000	0
Gross Liability	(27,309,000)	(7,391,000)
Collateral Netted	5,030,000	530,000
Net Asset (Liability) on Balance Sheet	(21,648,000)	(6,861,000)
Other Noncurrent Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	3,996,000	4,426,000
Gross Liability	(14,760,000)	(21,292,000)
Collateral Netted	5,214,000	13,427,000
Net Asset (Liability) on Balance Sheet	$ (5,550,000)	$ (3,439,000)

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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