Commitments and Contingencies (Commitments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020
Long-term Purchase Commitment [Line Items]
aircraft purchase deposit	$ 5,100		$ 5,100
Long-term Purchase Commitment, Amount			277,400
total government grant awarded	40,000		40,000		$ 37,400	$ 75,800
Income Tax (Expense) Benefit, Continuing Operations, Government Grants	38,274	$ 9,821	66,304	$ 9,821
unrecognized government grants received	$ 45,400		$ 45,400