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.

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of all derivative assets designated as fair value hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

+ Details

Name:	us-gaap_FairValueHedgeAssetsAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of all derivative liabilities designated as fair value hedging instruments.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Details

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- Details

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- Details

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- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
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Fair Value Measurements (Schedule of Fair Value of Fuel Hedge Contracts Balance Sheet Location) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivatives Fair Value [Line Items]
Fair value hedge assets	$ 2,293
Fair value hedge liabilities		$ 4,388
Derivatives Designated as Hedging Instruments [Member] \| Other Current Assets [Member] \| Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Fair value hedge assets	546
Derivatives Not Designated as Hedging Instruments [Member]” \| Other Current Assets [Member] \| Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Fair value hedge assets	$ 1,747
Derivatives Not Designated as Hedging Instruments [Member]” \| Accrued Expenses [Member] \| Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Fair value hedge liabilities		$ 4,388