Commitments and Contingencies - Aircraft Purchase and Lease Commitments (Details) - Future aircraft purchase commitments - aircraft	Sep. 30, 2016	Jun. 30, 2016
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	279
B-737-900ER
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	55
B-787-8
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	18
A321-200
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	71
A321-200 | Airbus
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required		37
A330-300
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	2
A330-900neo
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	25
A350-900
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	25
CS100
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	75
Aircraft purchase commitment with purchase options	50
E190-100
Unrecorded Unconditional Purchase Obligation
Aircraft purchase commitments, minimum quantity required	8