AOCI - Schedule of AOCI Components (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Fuel derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ (56)
Changes in Fair Value	87
Ending Balance	42
Interest rate derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	0
Changes in Fair Value	(15)
Reclassification to earnings	1
Ending Balance	(14)
Defined Benefit Plan Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	58
Changes in Fair Value	0
Reclassification to earnings	0
Ending Balance	58
Other comprehensive income other changes net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	25
Changes in Fair Value	14
Reclassification to earnings	0
Ending Balance	39
Deferred Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(7)
Changes in Fair Value	(19)
Reclassification to earnings	(3)
Ending Balance	(29)
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	20
Changes in Fair Value	67
Reclassification to earnings	9
Ending Balance	96
Reclassification out of Accumulated Other Comprehensive Income \| Fuel derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to earnings	$ 11

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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