Benefit Plans (Components of net periodic cost (benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Settlement loss			$ 84
Curtailment gain			(86)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 4	9
Interest cost on projected benefit obligation	113	112	132
Expected return on plan assets	(160)	(174)	(191)
Amortization of net actuarial (gain) loss	37	34	25
Settlement loss	0	0	84
Net periodic (benefit) cost	(10)	(24)	59
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost on projected benefit obligation	0	1	1
Amortization of prior service credit	(2)	(3)	(10)
Amortization of net actuarial (gain) loss	0	1	1
Curtailment gain	0	0	(86)
Net periodic (benefit) cost	$ (2)	$ (1)	$ (94)