Legal Matters (Details) (SkyWest Airlines and ExpressJet v. Delta, USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Dec. 31, 2007	Dec. 31, 2010	Mar. 31, 2013	Oct. 18, 2011
SkyWest Airlines and ExpressJet v. Delta
Legal Matters
Amount of receivables withheld from weekly scheduled wire payments to SkyWest Airlines and Atlantic Southeast	$ 25
Withheld receivables recognized as revenue by the entity			31.7
Amount that the settlement offered by the reporting entity was less than the cumulative amount of withheld receivables recognized as revenue by the reporting entity		5.9
Receivables written off by the entity		5.9
Minimum amount of possible damages			0	4.5
Settlement amount accrued			3.0
Reasonably possible loss related to dispute, maximum			$ 25.8