Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2011
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In January 2011, we adopted the remaining provisions of authoritative guidance issued in 2010 which requires enhanced disclosures for fair value measurements. The remaining provisions of this guidance became effective for our fiscal year 2011 interim and annual consolidated financial statements and require entities to present information about purchases, sales, issuances and settlements of financial instruments measured at fair value within the third level of the fair value hierarchy on a gross basis. See Note 9. Fair Value Measurements and Derivative Instruments for our disclosures required under this guidance. In January 2011, we also adopted the remaining provisions of authoritative guidance issued in 2010 which requires enhanced and disaggregated disclosures about the credit quality of financing receivables and the allowance for credit losses. The remaining provisions of this guidance became effective for our fiscal year 2011 interim and annual consolidated financial statements and require entities to disclose reporting period activity for financing receivables and the allowance for credit losses. The adoption of this guidance did not have an impact on our consolidated financial statements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In April 2011, authoritative guidance was issued to clarify when a modification or restructuring of a receivable constitutes a troubled debt restructuring. In evaluating whether such a modification or restructuring constitutes a troubled debt restructuring, a creditor must separately conclude that two conditions exist: (1) the modification or restructuring constitutes a concession and (2) the debtor is experiencing financial difficulties. The guidance will be effective for our interim and annual reporting periods beginning after June 15, 2011 and will be applied retrospectively to the beginning of the annual period of adoption. The adoption of this newly issued guidance is not expected to have a material impact on our consolidated financial statements. In May 2011, authoritative guidance was issued to achieve consistent fair value measurements and to clarify certain disclosure requirements for fair value measurements. The new guidance includes clarification about when the concept of highest and best use is applicable to fair value measurements, requires quantitative disclosures about inputs used and qualitative disclosures about the sensitivity of recurring Level 3 measurements, and requires the classification of all assets and liabilities measured at fair value in the fair value hierarchy including those assets and liabilities which are not recorded at fair value but for which fair value is disclosed. The guidance will be effective for our interim and annual reporting periods beginning after December 15, 2011. We are evaluating the impact of the adoption of this newly issued guidance but we do not expect it to have a material impact on our consolidated financial statements. In June 2011, authoritative guidance was issued on the presentation of comprehensive income. Specifically, the guidance allows an entity to present components of net income and other comprehensive income in one continuous statement, referred to as the statement of comprehensive income, or in two separate but consecutive statements. The new guidance eliminates the current option to report other comprehensive income and its components in the statement of changes in equity. This guidance will be applied retrospectively and will be effective for our interim and annual reporting periods beginning after December 15, 2011. We expect to add a new primary consolidated statement of other comprehensive income which will immediately follow our consolidated statements of operations to our filings when applicable.
Reclassifications	Reclassifications For the six months ended June 30, 2010, $7.3 million has been reclassified in the consolidated statement of cash flows from other, net within net cash flows provided by operating activities to (gain) loss on fuel call options within net cash flows provided by operating activities in order to conform to the current year presentation.
Other	Other Revenues and expenses include taxes assessed by governmental authorities that are directly imposed on a revenue-producing transaction between a seller and a customer. The amounts included on a gross basis in our consolidated statement of operations were $103.2 million and $94.1 million for the second quarters of 2011 and 2010, respectively, and $198.9 million and $175.4 million for the six months ended June 30, 2011 and 2010, respectively.