Commitments and Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Airline Capacity Purchase Arrangements [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Aircraft Purchase Commitments, Total	$ 8,015
B-737-900ER [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required	100
B-787-8 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required	18
CRJ-900 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required	56
MD-90 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required	2
A319-100 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number Of Aircraft Not Included In Aircraft Purchase Commitments	5
A320-200 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number Of Aircraft Not Included In Aircraft Purchase Commitments	2
B-717-200 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Other Aircraft Commitments	88
Bombardier Aerospace [Member] | CRJ-900 [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required	40