Benefit Plans (Components of net periodic cost (benefit)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 3
Interest cost on projected benefit obligation	33	30
Expected return on plan assets	(48)	(45)
Amortization of net actuarial (gain) loss	6	12
Net periodic cost (benefit)	(6)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service credit	(4)	(4)
Net periodic cost (benefit)	$ (4)	$ (4)