Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Gross Asset	$ 35,123,000	$ 43,222,000
Gross Liability	(145,084,000)	(82,203,000)
Collateral Netted	26,395,000	10,148,000
Net Asset (Liability) on Balance Sheet	(83,566,000)	(28,833,000)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	27,090,000	6,770,000
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	(695,000)	3,378,000
Other Current Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	36,000
Gross Liability	(103,000)
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	(67,000)
Other Current Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	238,000
Gross Liability	(32,967,000)	(9,379,000)
Collateral Netted	12,967,000	1,316,000
Net Asset (Liability) on Balance Sheet	(20,000,000)	(7,825,000)
Other Current Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	51,000	34,760,000
Gross Liability	(2,590,000)	(41,241,000)
Collateral Netted	0	3,378,000
Net Asset (Liability) on Balance Sheet	(2,539,000)	(3,103,000)
Other Current Assets [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		97,000
Gross Liability		0
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		97,000
Other Current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		589,000
Gross Liability		0
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		589,000
Other Current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	28,964,000	416,000
Gross Liability	(26,503,000)	(245,000)
Collateral Netted	(695,000)	0
Net Asset (Liability) on Balance Sheet	1,766,000	171,000
Other Property And Investments Net And Other Non-current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	6,072,000	6,369,000
Gross Liability	(3,626,000)	(5,446,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	2,446,000	923,000
Other Noncurrent Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	725,000
Gross Liability	(79,271,000)	(24,677,000)
Collateral Netted	14,123,000	5,454,000
Net Asset (Liability) on Balance Sheet	(65,148,000)	(18,498,000)
Other Noncurrent Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	28,000
Gross Liability	(24,000)	(1,215,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	$ (24,000)	$ (1,187,000)

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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