Benefit Plans (Components of net periodic cost (benefit)) (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, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 3	$ 9	$ 9
Interest cost on projected benefit obligation	30	34	90	101
Expected return on plan assets	(45)	(43)	(135)	(128)
Amortization of net actuarial (gain) loss	10	10	34	29
Settlement loss	3		3
Net periodic cost (benefit)	1	4	1	11
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation		1	1	2
Amortization of prior service credit	(4)	(4)	(13)	(13)
Amortization of net actuarial (gain) loss	1		1
Net periodic cost (benefit)	$ (3)	$ (3)	$ (11)	$ (11)