Leased Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Leased Assets [Line Items]
Gross rental expense	$ 400	$ 417	$ 415
Sublease rental income	(43)	(53)	(61)
Rent expense, net	357	364	354
Capital leases, minimum lease payments, Next Twelve months	16
Capital leases, minimum lease payments, Due in Two Years	13
Capital leases, minimum lease payments, Due in Three Years	11
Capital leases, minimum lease payments, Due in Four Years	9
Capital leases, minimum lease payments, Due in Five Years	7
Capital leases, minimum lease payments, Due Thereafter	40
Capital leases, minimum lease payments	96
Capital leases, imputed interest, Next Twelve Months	(4)
Capital leases, imputed interest, Due in Two Years	(3)
Capital leases, imputed interest, Due in Three Years	(3)
Capital leases, imputed interest, Due in Four Years	(3)
Capital leases, imputed interest, Due in Five Years	(3)
Capital leases, imputed interest, Due Thereafter	(18)
Capital leases, imputed interest	(34)
Capital leases. present value, Next Twelve Months	12
Capital leases. present value, Due in Two Years	10
Capital leases. present value, Due in Three Years	8
Capital leases. present value, Due in Four Years	6
Capital leases. present value, Due in Five Years	4
Capital leases. present value, Due Thereafter	22
Capital leases. present value	62
Operating leases, minimum lease payments, Next Twelve Months	326
Operating leases, minimum lease payments, Due in Two Years	259
Operating leases, minimum lease payments, Due in Three Years	201
Operating leases, minimum lease payments, Due in Four Years	144
Operating leases, minimum lease payments, Due in Five Years	104
Operating leases, minimum lease payments, Due Thereafter	326
Operating leases, minimum lease payments	1,360
Operating leases, minimum sublease rentals, Next Twelve Months	(45)
Operating leases, minimum sublease rentals, in Two Years	(35)
Operating leases, minimum sublease rentals, in Three Years	(25)
Operating leases, minimum sublease rentals, in Four Years	(14)
Operating leases, minimum sublease rentals, in Five Years	(6)
Operating leases, minimum sublease rentals, Thereafter	(9)
Operating leases, minimum sublease rentals	(134)
Operating leases, Next Twelve Months	281
Operating leases, Due in Two Years	224
Operating leases, Due in Three Years	176
Operating leases, Due in Four Years	130
Operating leases, Due in Five Years	98
Operating leases, Due Thereafter	317
Operating leases	1,226
Operating leases, imputed interest	(274)
Operating leases, present value	$ 952