Hedging Activities - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2016 USD ($) gal	Dec. 31, 2015 USD ($)
Derivatives And Hedging Activities [Line Items]
Percentage of projection for hedging financial instruments for the remainder of 2016	13.00%
Volume of fuel hedging for the remainder of 2016 \| gal	126,000,000
Fuel hedges expiration date	2016-12
Cash Flow Hedging
Derivatives And Hedging Activities [Line Items]
Percentage of projection of European euro for hedging financial instruments for remainder of 2016	16.00%
Fair value of derivative liability	$ 4	$ 124
Percentage of projection of Japanese yen for hedging financial instruments for remainder of 2016	18.00%
Foreign Currency Derivatives Liability , Net
Derivatives And Hedging Activities [Line Items]
Fair value of derivative liability	$ 1
Fuel Derivative Instruments
Derivatives And Hedging Activities [Line Items]
Fuel hedge collateral deposits		$ 26

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

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

Cash Collateral Posted For Derivatives Liability

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- Definition

Derivative Instrument Expiry Date

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- Definition

Derivatives And Hedging Activities [Line Items]

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- Definition

The percentage of projected European euro denominated net cash inflows that are hedged with foreign currency derivatives

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- Definition

Hedging Contract As Percentage Of Projected Japanese Yen Net Cash Inflow

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- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

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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.

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