Airtran Acquisition and Related Matters (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Combinations [Abstract]
Acquisition and integration	$ 39	$ 126	$ 86

Costs incurred to effect a business combination which have been expensed during the period. Such costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

No definition available.

Name:	us-gaap_BusinessCombinationIntegrationRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration