Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension settlement charges	$ 22	$ 0
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	4
Interest cost	7	10
Amortization of actuarial losses	5	4
Amortization of prior service credit	(13)	(2)
Net periodic pension/other postretirement benefit cost	1	16
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	13
Interest cost	24	42
Expected return on plan assets	(34)	(67)
Amortization of actuarial losses	19	30
Amortization of prior service credit	0	0
Pension settlement charges	22	0
Net periodic pension/other postretirement benefit cost	$ 40	$ 18