New Accounting Pronouncements (Details) $ in Millions	Jun. 30, 2017 USD ($) aircraft
New Accounting Pronouncements or Change in Accounting Principle
Aircraft under operating lease | aircraft	78
Rapid Rewards Frequent Flier Liability | $	$ 62
Minimum
New Accounting Pronouncements or Change in Accounting Principle
Estimated Impact	20
Maximum
New Accounting Pronouncements or Change in Accounting Principle
Estimated Impact	25