Commitments and Contingencies (Commitments) (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($)
Long-term Purchase Commitment [Line Items]
aircraft purchase deposit	$ 23.2
Long-term Purchase Commitment, Amount	$ 369.1

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.

No definition available.

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