Benefit Plans (Components of net periodic cost (benefit)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain				$ (86)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 1	$ 4	4
Interest cost on projected benefit obligation	28	33	56	66
Expected return on plan assets	(44)	(48)	(87)	(96)
Amortization of net actuarial (gain) loss	10	7	19	13
Net periodic (benefit) cost	(4)	(7)	(8)	(13)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	0	1	0	1
Amortization of net actuarial (gain) loss	1	0	1	0
Amortization of prior service credit	(1)	(5)	(1)	(9)
Curtailment gain	0	(86)	0	(86)
Net periodic (benefit) cost	$ 0	$ (90)	$ 0	$ (94)