Employee Retirement Benefits (Net Periodic Benefit Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 37	$ 39	$ 37
Interest cost	72	72	66
Expected return on plan assets	(73)	(69)	(60)
Other	30	12	9
Net periodic benefit cost	66	54	52
Other Postretirement Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	6	6	6
Interest cost	9	9	9
Expected return on plan assets	0	0	0
Other	(3)	(7)	(2)
Net periodic benefit cost	$ 12	$ 8	$ 13