Lease Obligations (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Mainline [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due, Current	$ 926
Operating Leases, Future Minimum Payments, Due in Two Years	912
Operating Leases, Future Minimum Payments, Due in Three Years	862
Operating Leases, Future Minimum Payments, Due in Four Years	765
Operating Leases, Future Minimum Payments, Due in Five Years	677
Operating Leases, Future Minimum Payments, Due Thereafter	6,660
Operating Leases, Future Minimum Payments Due	10,802
Regional Carrier [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due, Current	536
Operating Leases, Future Minimum Payments, Due in Two Years	529
Operating Leases, Future Minimum Payments, Due in Three Years	518
Operating Leases, Future Minimum Payments, Due in Four Years	506
Operating Leases, Future Minimum Payments, Due in Five Years	449
Operating Leases, Future Minimum Payments, Due Thereafter	928
Operating Leases, Future Minimum Payments Due	3,466
Reporting Entity [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due, Current	1,462
Operating Leases, Future Minimum Payments, Due in Two Years	1,441
Operating Leases, Future Minimum Payments, Due in Three Years	1,380
Operating Leases, Future Minimum Payments, Due in Four Years	1,271
Operating Leases, Future Minimum Payments, Due in Five Years	1,126
Operating Leases, Future Minimum Payments, Due Thereafter	7,588
Operating Leases, Future Minimum Payments Due	$ 14,268