Fair Value Accounting (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Assets:
Cash equivalents	$ 134.8	$ 246.6
Restricted cash	224.0	240.3
Fuel derivative instruments	0.1
Total assets	359.6	487.6
Interest rate hedges
Fuel derivative instruments		0.1
Total liabilities	53.0	56.9
Equity Call Agreement [Member]
Assets:
Equity call agreement with TRIP Holdings equity investor	0.7	0.7
Interest rate hedges
Equity put agreement with TRIP Holdings equity investor	2.6	3.1
Wholly Owned Subsidiaries [Member]
Interest rate hedges
Interest rate hedges	46.2	48.9
TRIP Holdings [Member]
Interest rate hedges
Interest rate hedges	4.2	4.8
Level 1 [Member]
Assets:
Cash equivalents	134.8	246.6
Restricted cash	224.0	240.3
Total assets	358.8	486.9
Interest rate hedges
Fuel derivative instruments
Total liabilities
Level 1 [Member] \| Equity Call Agreement [Member]
Interest rate hedges
Equity put agreement with TRIP Holdings equity investor
Level 1 [Member] \| Wholly Owned Subsidiaries [Member]
Interest rate hedges
Interest rate hedges
Level 1 [Member] \| TRIP Holdings [Member]
Interest rate hedges
Interest rate hedges
Level 2 [Member]
Assets:
Cash equivalents
Restricted cash
Fuel derivative instruments	0.1
Total assets	0.1
Interest rate hedges
Fuel derivative instruments		0.1
Total liabilities	50.4	53.8
Level 2 [Member] \| Equity Call Agreement [Member]
Assets:
Equity call agreement with TRIP Holdings equity investor
Level 2 [Member] \| Wholly Owned Subsidiaries [Member]
Interest rate hedges
Interest rate hedges	46.2	48.9
Level 2 [Member] \| TRIP Holdings [Member]
Interest rate hedges
Interest rate hedges	4.2	4.8
Level 3 [Member]
Assets:
Total assets	0.7	0.7
Interest rate hedges
Total liabilities	2.6	3.1
Level 3 [Member] \| Equity Call Agreement [Member]
Assets:
Equity call agreement with TRIP Holdings equity investor	0.7	0.7
Interest rate hedges
Equity put agreement with TRIP Holdings equity investor	$ 2.6	$ 3.1

Investments held in fuel commodities.

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Fuel commodities liabilities fair value disclosure.

+ References

No definition available.

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+ References

No definition available.

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This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher FASB

-Name Accounting Standards Codification

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7, 8, 9, 10

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-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 Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 8

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-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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Fair value as of the balance sheet date of all derivative liabilities designated as interest rate fair value hedging instruments.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 17

-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 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959

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