Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Gross Asset	$ 46,766,000	$ 61,191,000
Gross Liability	(144,548,000)	(150,381,000)
Collateral Netted	51,337,000	44,758,000
Net Asset (Liability) on Balance Sheet	(46,445,000)	(44,432,000)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	41,570,000	34,900,000
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	9,767,000	9,858,000
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		5,000
Gross Liability		(28,000)
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		(23,000)
Other Current Assets [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	187,000
Gross Liability	0
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	187,000
Other Current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	5,626,000	3,393,000
Gross Liability	(208,000)	0
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	5,418,000	3,393,000
Other Current Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	168,000	18,682,000
Gross Liability	(11,000)	(16,787,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	157,000	1,895,000
Other Current Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	0
Gross Liability	(78,077,000)	(15,756,000)
Collateral Netted	41,570,000	9,731,000
Net Asset (Liability) on Balance Sheet	(36,507,000)	(6,025,000)
Non-Current Interest Rate Swap Derivative Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	3,951,000
Gross Liability	(336,000)	(57,825,000)
Collateral Netted	0	25,169,000
Net Asset (Liability) on Balance Sheet	(336,000)	(28,705,000)
Other Property And Investments Net and Other Non-current Assets[Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	5,676,000	5,754,000
Gross Liability	(1,645,000)	(397,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	4,031,000	5,357,000
Current Utility Energy Commodity Derivative Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	22,577,000	16,335,000
Gross Liability	(36,716,000)	(29,598,000)
Collateral Netted	5,831,000	6,228,000
Net Asset (Liability) on Balance Sheet	(8,308,000)	(7,035,000)
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	12,532,000	13,071,000
Gross Liability	(27,555,000)	(29,990,000)
Collateral Netted	3,936,000	3,630,000
Net Asset (Liability) on Balance Sheet	$ (11,087,000)	$ (13,289,000)