DERIVATIVE INSTRUMENTS - FUEL HEDGE CONTRACTS (DETAILS) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Raw or into-plane fuel cost	$ 337.4	$ 233.8	$ 969.5	$ 651.9
(Gains) or losses in value and settlements of fuel hedge contracts	82.7	(12.9)	42.6	31.3
Aircraft fuel expense	420.1	220.9	1,012.1	683.2
Payments for (Proceeds from) Hedge, Investing Activities	$ 1.6	$ 3.8	$ 30.6	$ 2.1

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.

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- Definition

Fuel costs incurred that are directly related to goods produced and sold and services rendered during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2(a),(d))

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- Definition

The cost for fuel, incurred during the period, before considering the impacts of any related hedging activities.

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- Definition

Gain (loss) incurred in oil and gas hedging activities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5618551-113959

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- Definition

The cash outflow or inflow for a financial contract that meets the hedge criteria as either a cash flow hedge, fair value hedge, or hedge of a net investment in a foreign operation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 27

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3581-108585

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 14

-Footnote 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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-Section 45

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-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3095-108585

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3098-108585

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