Summary of Significant Accounting Policies (Details 3)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies
Number of operating segments	1
United States
Passengers ticket revenue, percentage
Passengers ticket revenue, percentage	51.00%	51.00%	55.00%
All other countries
Passengers ticket revenue, percentage
Passengers ticket revenue, percentage	49.00%	49.00%	45.00%

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

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Period Type:	duration