Benefit Plans (Components of net periodic cost (benefit)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain				$ (86)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 3	$ 4	7
Interest cost on projected benefit obligation	29	33	85	99
Expected return on plan assets	(44)	(48)	(131)	(144)
Amortization of net actuarial (gain) loss	7	6	26	19
Net periodic (benefit) cost	(8)	(6)	(16)	(19)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	0	0	0	1
Amortization of prior service credit	(1)	0	(2)	(9)
Amortization of net actuarial (gain) loss	0	0	1	0
Curtailment gain	0	0	0	(86)
Net periodic (benefit) cost	$ (1)	$ 0	$ (1)	$ (94)