Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Materials and supplies	$ 43,202	$ 41,493
Fuel stock	4,798	4,843
Natural gas stored	1,259	11,739
Total	$ 49,259	$ 58,075

No definition available.

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- Definition

Carrying amount as of the balance sheet date of natural gas stored underground in depleted gas reservoirs, aquifers, or salt caverns to meet seasonal and peak load demands, and also as insurance against unforeseen supply disruptions, and deemed to be a current asset because it is expected to be used within twelve months or in the normal operating cycle.

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+ Details

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- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 35
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=68049868&loc=d3e3927-108312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

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Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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Amount before valuation and LIFO reserves of other inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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