Gallons of diesel fuel purchased annually.

No definition available.

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- Definition

Value of trading portfolio realized at a certain point in time gains (losses)

+ References

No definition available.

+ Details

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- Definition

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

The average strike price on the group of price risk option contracts such as put options or call options.

+ References

No definition available.

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- Definition

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (d)(2)

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-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 13

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The percentage of expected requirements covered by the aggregate notional amount of derivative contracts expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract as a percentage of expected need.

+ References

No definition available.

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- Definition

The estimated net amount of unrealized gains or losses on price risk cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

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- Definition

Amount of gain (loss) resulting from the difference between the acquisition price and the selling price or fair value of trading assets and trading liabilities, conducted separately from customer trading activities. Includes, but is not limited to, changes in fair value of trading assets and trading liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(e))

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-Topic 940

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-Topic 940

-SubTopic 320

-Section 45

-Paragraph 5

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-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4F

-Subparagraph (a)

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Derivatives (Narrative) (Details) gal in Millions, $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) gal $ / option	Sep. 30, 2014 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($) gal $ / option	Sep. 30, 2014 USD ($)	Dec. 31, 2016 USD ($) $ / option	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Current liability for the obligation to return cash collateral	$ 2.9			$ 2.9			$ 2.4
Gain on derivative contracts designated as hedge instruments in cash flow hedges to be reclassified from OCI into earnings during the next twelve months	0.9			0.9
Net unrealized and realized gains (losses) related to trading portfolio	$ 4.4	$ 1.9		$ 3.3	$ 5.4
Scenario, Forecast [Member]
Derivative [Line Items]
Value of trading portfolio realized			$ 1.4			$ 5.3
Not Designated as Hedging Instrument [Member] \| Heating Oil [Member]
Derivative [Line Items]
Derivative, average price risk option strike price \| $ / option	3.13			3.13
Not Designated as Hedging Instrument [Member] \| Heating Oil [Member] \| Scenario, Forecast [Member]
Derivative [Line Items]
Derivative, average price risk option strike price \| $ / option						2.26
Not Designated as Hedging Instrument [Member] \| Diesel Purchases [Member]
Derivative [Line Items]
Percent of expected requirements covered	100.00%			100.00%
Not Designated as Hedging Instrument [Member] \| Diesel Purchases [Member] \| Scenario, Forecast [Member]
Derivative [Line Items]
Percent of expected requirements covered						67.00%
Not Designated as Hedging Instrument [Member] \| Diesel Purchases [Member] \| Heating Oil [Member]
Derivative [Line Items]
Quantities under derivative contracts \| gal	54			54
Not Designated as Hedging Instrument [Member] \| Diesel Purchases [Member] \| Minimum [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal				55
Not Designated as Hedging Instrument [Member] \| Diesel Purchases [Member] \| Maximum [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal				65