Benefit Plans and Other Postretirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Benefit Plans and Other Postretirement Benefits
Litigation Settlement, Amount			$ 12
Annual periodic pension cost
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	$ 0	$ (21)	0
Pension Benefits
Annual periodic pension cost
Service cost benefits earned	(30)	(32)	(30)
Interest cost on benefit obligation	43	53	53
Expected return on plan assets	(60)	(62)	(62)
Amortization of unrecognized net loss/(gain)	2	2	(6)
Net periodic benefit cost	15	25	15
Pension and other post retirement benefit obligations
Benefit obligation at January 1	1,196	1,305
Service cost	30	32	30
Interest cost	43	53	53
Plan amendments	0	0
Actuarial loss/(gain)	40	(120)
Employee and retiree contributions	0	0
Benefit payments	(68)	(74)
Defined Benefit Plan, Curtailments	0	0
Benefit obligation at December 31	1,241	1,196	1,305
Fair value of plan assets for pension and other post retirement benefit
Fair value of plan assets at January 1	916	988
Actual return on plan assets	72	(26)
Employee and retiree contributions	0	0
Employer contributions	33	28
Benefit payments	(68)	(74)
Fair value of plan assets at December 31	953	916	988
Funded status at December 31 — excess of obligation over assets	(288)	(280)
Other Postretirement Benefits
Annual periodic pension cost
Service cost benefits earned	(2)	(3)	(3)
Interest cost on benefit obligation	6	9	9
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(5)	(5)	(17)
Amortization of unrecognized net loss/(gain)	0	1	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0	(14)	0
Net periodic benefit cost	3	(6)	(5)
Pension and other post retirement benefit obligations
Benefit obligation at January 1	178	238
Service cost	2	3	3
Interest cost	6	9	9
Plan amendments	(42)	(6)
Actuarial loss/(gain)	(2)	(31)
Employee and retiree contributions	3	2
Benefit payments	(17)	(12)
Defined Benefit Plan, Curtailments	0	25
Benefit obligation at December 31	128	178	238
Fair value of plan assets for pension and other post retirement benefit
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Employee and retiree contributions	3	2
Employer contributions	14	10
Benefit payments	(17)	(12)
Fair value of plan assets at December 31	0	0	$ 0
Funded status at December 31 — excess of obligation over assets	(128)	$ (178)
Scenario, Plan [Member] | Pension Benefits
Benefit Plans and Other Postretirement Benefits
Expected contribution to the Company's pension plans in 2014	$ 36