Leases (Schedule of Future Minimum Lease Payments for Capital and Operating Leases) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 296	[1]
Operating Leases, Future Minimum Payments, Due in Two Years	237	[1]
Operating Leases, Future Minimum Payments, Due in Three Years	178	[1]
Operating Leases, Future Minimum Payments, Due in Four Years	278	[1]
Operating Leases, Future Minimum Payments, Due in Five Years	88	[1]
Operating Leases, Future Minimum Payments, Due Thereafter	234	[1]
Operating Leases, Future Minimum Payments Due, Total	1,311	[1]
Capital Leases, Future Minimum Payments Due, Next Twelve Months	56
Capital Leases, Future Minimum Payments Due in Two Years	44
Capital Leases, Future Minimum Payments Due in Three Years	30
Capital Leases, Future Minimum Payments Due in Four Years	20
Capital Leases, Future Minimum Payments Due in Five Years	16
Capital Leases, Future Minimum Payments Due Thereafter	210
Capital Leases, Future Minimum Payments Due, Total	376
Capital Leases, Future Minimum Payments, Interest Included in Payments	(148)
Capital Lease Obligations, Total	228
Capital Lease Obligations, Current	(42)
Capital Lease Obligations, Noncurrent	$ 186

[1] Minimum lease payments have not been reduced by minimum sublease rentals due in the future of $26 million.