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Financial Derivative Instruments - Fuel Hedging (Details) gal in Millions | Dec. 31, 2017 gal | [1]
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2018 |
Volume of Fuel Hedging [Line Items] |
Fuel Hedged (in gallons) | 1,647
2019 |
Volume of Fuel Hedging [Line Items] |
Fuel Hedged (in gallons) | 1,377
2020 |
Volume of Fuel Hedging [Line Items] |
Fuel Hedged (in gallons) | 685
Beyond 2020 |
Volume of Fuel Hedging [Line Items] |
Fuel Hedged (in gallons) | 315
[1] | Due to the types of derivatives utilized by the Company and different price levels of those contracts, these volumes represent the maximum economic hedge in place and may vary significantly as market prices fluctuate.

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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 + Details
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