Benefit Plans (Components of net periodic cost (benefit)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain			$ 86
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	3	4	6
Interest cost on projected benefit obligation	33	30	66	60
Expected return on plan assets	(48)	(45)	(96)	(90)
Amortization of net actuarial (gain) loss	7	12	13	24
Net periodic cost (benefit)	(7)		(13)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	1	1	1	1
Amortization of prior service credit	(5)	(5)	(9)	(9)
Curtailment gain	86		86
Net periodic cost (benefit)	$ (90)	$ (4)	$ (94)	$ (8)