Leases (Schedule of Future Minimum Lease Payments for Capital and Operating Leases) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 288	[1]
Operating Leases, Future Minimum Payments, Due in Two Years	225	[1]
Operating Leases, Future Minimum Payments, Due in Three Years	162	[1]
Operating Leases, Future Minimum Payments, Due in Four Years	117	[1]
Operating Leases, Future Minimum Payments, Due in Five Years	88	[1]
Operating Leases, Future Minimum Payments, Due Thereafter	222	[1]
Operating Leases, Future Minimum Payments Due, Total	1,102	[1]
Capital Leases, Future Minimum Payments Due, Next Twelve Months	48
Capital Leases, Future Minimum Payments Due in Two Years	34
Capital Leases, Future Minimum Payments Due in Three Years	23
Capital Leases, Future Minimum Payments Due in Four Years	19
Capital Leases, Future Minimum Payments Due in Five Years	15
Capital Leases, Future Minimum Payments Due Thereafter	245
Capital Leases, Future Minimum Payments Due, Total	384
Capital Leases, Future Minimum Payments, Interest Included in Payments	(157)
Capital Lease Obligations, Total	227
Capital Lease Obligations, Current	(42)
Capital Lease Obligations, Noncurrent	$ 185

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