Lease Obligations (Narrative) (Details) (USD $) In Billions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Leases, Rent Expense	$ 1.1	$ 1.1	$ 1.1
Capital Lease Expense [Member] | Mainline [Member]
Number of Aircraft Operated	109
Operating Lease Expense [Member] | Mainline [Member]
Number of Aircraft Operated	68
Operating Lease Expense [Member] | Regional Carrier [Member]
Number of Aircraft Operated	568