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New Accounting Pronouncements (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) aircraft	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) aircraft	Sep. 30, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Aircraft rentals	$ 41	$ 51	$ 121	$ 158
Aircraft under operating lease | aircraft	51		51
Net Present Value Aircraft Operating Leases	$ 775		$ 775
ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	4		$ 10
AOCI Including Portion Attributable to Noncontrolling Interest
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 20
B-717-200
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Aircraft under operating lease | aircraft	76		76

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Net Present Value Aircraft Operating Leases

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- Definition

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- Definition

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- Definition

The number of units (items of property) under operating lease arrangements.

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