EBPs Obligation Rollforward (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits [Member]
Change in benefit obligation:
Service cost	$ 11	$ 10	$ 33	$ 29
Interest cost	12	14	38	42
Other Postretirement Benefits [Member]
Change in benefit obligation:
Service cost	1	1	2	2
Interest cost	2	4	8	10
Plan amendment			(59)
Actuarial loss (gain)			$ (62)