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Hedging Activities - Additional Information (Detail) - Fuel Contract | 9 Months Ended
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Sep. 30, 2017 Contract
Derivatives And Hedging Activities [Line Items] |
Fuel hedging contracts outstanding | 0
Cash Flow Hedging | Designated as Hedging Instrument |
Derivatives And Hedging Activities [Line Items] |
Fuel hedges expiration date | 2016-12

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- Definition The number of derivative instruments of a particular group held by the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959 + Details
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