Commitments and Contingencies - Aircraft Purchase Commitments by Fleet Type (Details) - Future aircraft purchase commitments	Dec. 31, 2020 aircraft lease_commitment
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	224
A220-100
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	7
A220-300
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	45
A321-200
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	22
A321-200neo
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	100
A330-900neo
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	29
Number of lease commitments included in purchase commitment | lease_commitment	1
A350-900
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	20
CRJ-900
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	1