Benefit Plans (Components of net periodic cost (benefit)) (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 2	$ 0	$ 4
Interest cost on projected benefit obligation	28	28	56	56
Expected return on plan assets	(40)	(44)	(80)	(87)
Amortization of net actuarial (gain) loss	10	10	19	19
Net periodic (benefit) cost	$ (2)	$ (4)	$ (5)	$ (8)