Employee Benefit Plans Employee Benefit Plans (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 Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2	$ 4	$ 6
Interest cost	14	15	41	45
Expected return on plan assets	(19)	(19)	(56)	(56)
Net amortization	12	9	36	26
Net periodic benefit cost	8	7	25	21
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	6	5
Interest cost	6	7	19	21
Expected return on plan assets	(7)	(7)	(22)	(22)
Net amortization	2	1	6	3
Net periodic benefit cost	$ 3	$ 3	$ 9	$ 7