Employee Benefits Schedule of Defined Benefit Plan Disclosures (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets		$ 4	$ 5
Fair value of plan assets:
Benefit payments	$ (16)
As of January 1			550
Classification in consolidated balance sheet:
Noncurrent asset		(34)	(33)
Noncurrent liability		(281)	(259)
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		52	44
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets		4	5
Fair value of plan assets:
As of January 1		0	0
Pension Plans, Defined Benefit [Member]
Benefit obligation:
As of January 1		797	758	$ 777
Fair value of plan assets:
Service cost		16	18	15
Interest cost on benefit obligation		33	31	34
Participants’ contributions		0	0
Actuarial loss (gain)		26	(31)
Defined Benefit Plan, Special Termination Benefits		0	0
Benefit payments		(34)	(35)
Defined Benefit Plan, Administration Expenses		(2)	(2)
As of January 1		559	550	591
Unfunded position as of December 31		238	208
Net actuarial loss (gain) included in comprehensive income		21	13
Defined Benefit Plan, Amortization of Gains (Losses)		(14)	(20)	(17)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		0	0	0
Total Amounts included in comprehensive income		7	(7)
Defined Benefit Plan, Accumulated Benefit Obligation		714	681
Actual return on plan assets		45	(4)
Company contributions		0	0
Classification in consolidated balance sheet:
Noncurrent asset		0	0
Current liability		0	0
Noncurrent liability		(238)	(208)
Amounts included in AOCL:
Net actuarial loss		236	228
Prior service cost		0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		$ 236	$ 228
Assumptions used:
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate		4.17%	4.36%
Discount rate used to calculate benefit obligation		4.36%	4.02%
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%
Long-term rate of return on plan assets		7.50%	7.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets		7.50%	7.50%
Other Postretirement Benefit Plans [Member]
Benefit obligation:
As of January 1		$ 73	$ 81	83
Fair value of plan assets:
Service cost		2	2	2
Interest cost on benefit obligation		4	3	4
Participants’ contributions		2	2
Actuarial loss (gain)		(11)	(4)
Defined Benefit Plan, Special Termination Benefits		0	1
Benefit payments		(5)	(6)
Defined Benefit Plan, Administration Expenses		0	0
As of January 1		30	30	32
Unfunded position as of December 31		43	51
Net actuarial loss (gain) included in comprehensive income		(10)	0
Defined Benefit Plan, Amortization of Gains (Losses)		0	(1)	(1)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(1)	(1)	(1)
Total Amounts included in comprehensive income		(11)	(2)
Actual return on plan assets		1	(2)
Company contributions		2	4
Classification in consolidated balance sheet:
Noncurrent asset		0	0
Current liability		0	0
Noncurrent liability		(43)	(51)
Amounts included in AOCL:
Net actuarial loss		(2)	9
Prior service cost		1	1
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		$ (1)	$ 10
Assumptions used:
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate		3.75%	3.90%
Defined Benefit Plan Discount rate - upper range		4.23%	4.45%
Discount rate used to calculate benefit obligation		3.90%	3.07%
Defined Benefit Plan Cost Discount rate - upper range		4.45%	4.10%
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%
Long-term rate of return on plan assets		6.26%	6.29%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets		6.29%	6.37%
Non Qualified Benefit Plans [Member]
Benefit obligation:
As of January 1		$ 27	$ 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, Special Termination Benefits		0	0
Benefit payments		(2)	(2)
Defined Benefit Plan, Administration Expenses		0	0
As of January 1		16	15	15
Unfunded position as of December 31		11	12
Net actuarial loss (gain) included in comprehensive income		1	1
Defined Benefit Plan, Amortization of Gains (Losses)		(1)	(1)	(1)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		0	0	$ 0
Total Amounts included in comprehensive income		0	0
Defined Benefit Plan, Accumulated Benefit Obligation		27	27
Actual return on plan assets		1	0
Company contributions		2	2
Classification in consolidated balance sheet:
Noncurrent asset		(16)	(15)
Current liability		(2)	(2)
Noncurrent liability		(25)	(25)
Amounts included in AOCL:
Net actuarial loss		13	13
Prior service cost		0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		$ 13	$ 13
Assumptions used:
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate		4.17%	4.36%
Discount rate used to calculate benefit obligation		4.36%	4.02%