Employee Benefits Schedule of Defined Benefit Plan Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets	$ 5	$ 5
Fair value of plan assets:
As of January 1		629
Classification in consolidated balance sheet:
Noncurrent asset	(36)	(37)
Noncurrent liability	(307)	(284)
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets	0	0
Fair value of plan assets:
As of January 1	0	0
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets	0	0
Fair value of plan assets:
As of January 1	67	83
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets	5	5
Fair value of plan assets:
As of January 1	0	0
Pension Plans, Defined Benefit [Member]
Benefit obligation:
As of January 1	811	869	$ 797
Fair value of plan assets:
Service cost	19	17	16
Interest cost on benefit obligation	32	33	33
Participants’ contributions	0	0
Actuarial loss (gain)	(67)	60
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0	0
Benefit payments	(39)	(36)
Defined Benefit Plan, Plan Assets, Administration Expense	(3)	(2)
As of January 1	546	629	559
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(265)	(240)
Net actuarial loss (gain) included in comprehensive income	25	(4)
Defined Benefit Plan, Amortization of Gain (Loss)	(17)	(13)	(14)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	0
Total Amounts included in comprehensive income	8	(17)
Defined Benefit Plan, Accumulated Benefit Obligation	734	778
Actual return on plan assets	(50)	106
Company contributions	9	2
Classification in consolidated balance sheet:
Noncurrent asset	0	0
Current liability	0	0
Noncurrent liability	(265)	(240)
Amounts included in AOCL:
Net actuarial loss	226	218
Prior service cost	0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	$ 226	$ 218
Assumptions used:
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate	4.25%	3.65%
Discount rate used to calculate benefit obligation	3.65%	4.17%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Rate of Compensation Increase	3.65%	3.65%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.65%	3.65%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	7.00%	7.50%
Other Postretirement Benefit Plans [Member]
Benefit obligation:
As of January 1	$ 72	$ 78	73
Fair value of plan assets:
Service cost	2	2	2
Interest cost on benefit obligation	3	3	4
Participants’ contributions	2	2
Actuarial loss (gain)	(7)	3
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0	1
Benefit payments	(6)	(6)
Defined Benefit Plan, Plan Assets, Administration Expense	0	0
As of January 1	30	33	30
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(42)	(45)
Net actuarial loss (gain) included in comprehensive income	(4)	0
Defined Benefit Plan, Amortization of Gain (Loss)	0	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	(1)
Total Amounts included in comprehensive income	(4)	0
Actual return on plan assets	(2)	4
Company contributions	3	3
Classification in consolidated balance sheet:
Noncurrent asset	0	0
Current liability	0	0
Noncurrent liability	(42)	(45)
Amounts included in AOCL:
Net actuarial loss	(4)	(1)
Prior service cost	0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	$ (4)	$ (1)
Assumptions used:
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate	4.10%	3.42%
Defined Benefit Plan Discount rate - upper range	4.26%	3.70%
Discount rate used to calculate benefit obligation	3.42%	3.75%
Defined Benefit Plan Cost Discount rate - upper range	3.70%	4.23%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Rate of Compensation Increase	4.58%	4.58%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	4.58%	4.58%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	6.20%	6.26%
Non Qualified Benefit Plans [Member]
Benefit obligation:
As of January 1	$ 24	$ 27	27
Fair value of plan assets:
Service cost	0	0	0
Interest cost on benefit obligation	1	1	1
Participants’ contributions	0	0
Actuarial loss (gain)	(1)	1
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0	0
Benefit payments	(3)	(2)
Defined Benefit Plan, Plan Assets, Administration Expense	0	0
As of January 1	16	17	16
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(8)	(10)
Net actuarial loss (gain) included in comprehensive income	(1)	1
Defined Benefit Plan, Amortization of Gain (Loss)	(1)	(1)	(1)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0	$ 0
Total Amounts included in comprehensive income	(2)	0
Defined Benefit Plan, Accumulated Benefit Obligation	24	27
Actual return on plan assets	(1)	1
Company contributions	3	2
Classification in consolidated balance sheet:
Noncurrent asset	(16)	(17)
Current liability	(2)	(2)
Noncurrent liability	(22)	(25)
Amounts included in AOCL:
Net actuarial loss	11	13
Prior service cost	0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	$ 11	$ 13
Assumptions used:
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate	4.25%	3.65%
Discount rate used to calculate benefit obligation	3.65%	4.17%