Lease Obligations (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Mainline [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due, Current	$ 1,005	[1]
Operating Leases, Future Minimum Payments, Due in Two Years	949	[1]
Operating Leases, Future Minimum Payments, Due in Three Years	859	[1]
Operating Leases, Future Minimum Payments, Due in Four Years	736	[1]
Operating Leases, Future Minimum Payments, Due in Five Years	627	[1]
Operating Leases, Future Minimum Payments, Due Thereafter	6,414	[1]
Operating Leases, Future Minimum Payments Due	10,590	[1]
Regional Carrier [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due, Current	502
Operating Leases, Future Minimum Payments, Due in Two Years	484
Operating Leases, Future Minimum Payments, Due in Three Years	473
Operating Leases, Future Minimum Payments, Due in Four Years	423
Operating Leases, Future Minimum Payments, Due in Five Years	373
Operating Leases, Future Minimum Payments, Due Thereafter	1,001
Operating Leases, Future Minimum Payments Due	3,256
Reporting Entity [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due, Current	1,507
Operating Leases, Future Minimum Payments, Due in Two Years	1,433
Operating Leases, Future Minimum Payments, Due in Three Years	1,332
Operating Leases, Future Minimum Payments, Due in Four Years	1,159
Operating Leases, Future Minimum Payments, Due in Five Years	1,000
Operating Leases, Future Minimum Payments, Due Thereafter	7,415
Operating Leases, Future Minimum Payments Due	$ 13,846

[1] (1) Includes payments accounted for as construction obligations. See Note 5.