Commitments and Contingencies - Aircraft Purchase Commitments By Aircraft (Details) - Future aircraft purchase commitments	Mar. 31, 2020 aircraft lease_commitments
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	253
A220-100
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	14
A220-300
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	50
A321-200
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	27
A321-200neo
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	100
A330-900neo
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	32
Number of lease commitments included in purchase commitment | lease_commitments	2
A350-900
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	26
CRJ-900
Future Purchase Commitments
Aircraft purchase commitments, minimum quantity required	4