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Revenue Recognition Passenger Revenue (Details) - USD ($)
$ in Thousands
 1 Months Ended 6 Months Ended
Apr. 30, 2020
Jun. 30, 2021
Dec. 31, 2020
Jun. 30, 2020
Dec. 31, 2019
Revenue Recognition [Abstract]          
Contract with Customer, Liability, Forward Bookings   69.80%      
Contract with Customer, Liability, Credit Voucher Bookings   30.20%      
Revenue, Performance Obligation, Description of Timing   12 months      
Credit Voucher Term Expiration 2 years        
Air Traffic Liability, Recognized   $ 150,400      
Contract with Customer, Liability   $ 24,154 $ 21,841 $ 19,343 $ 15,613
Air Traffic Liability, Current     $ 307,500