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Employee Benefits Schedule of Defined Benefit Plan Disclosures (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items] |  |  |
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets | $ 5 | $ 4 |
Fair value of plan assets: |  |  |
Interest cost on benefit obligation | 3 |  |
As of January 1 |  | 559 |
Classification in consolidated balance sheet: |  |  |
Noncurrent asset | (37) | (34) |
Noncurrent liability | (284) | (281) |
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 | 83 | 52 |
Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Debt Securities— Domestic Government Other Postretirement Benefit Plan Assets | 5 | 4 |
Fair value of plan assets: |  |  |
As of January 1 | 0 | 0 |
Pension Plans, Defined Benefit [Member] |  |  |
Benefit obligation: |  |  |
As of January 1 | 869 | 797 | $ 758
Fair value of plan assets: |  |  |
Service cost | 17 | 16 | 18
Interest cost on benefit obligation | 33 | 33 | 31
Participants’ contributions | 0 | 0 |
Actuarial loss (gain) | 60 | 26 |
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits | 0 | 0 |
Benefit payments | (36) | (34) |
Defined Benefit Plan, Plan Assets, Administration Expense | (2) | (2) |
As of January 1 | 629 | 559 | 550
Unfunded position as of December 31 | 240 | 238 |
Net actuarial loss (gain) included in comprehensive income | (4) | 21 |
Defined Benefit Plan, Amortization of Gain (Loss) | (13) | (14) | (20)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | 0 | 0
Total Amounts included in comprehensive income | (17) | 7 |
Defined Benefit Plan, Accumulated Benefit Obligation | 778 | 714 |
Actual return on plan assets | 106 | 45 |
Company contributions | 2 | 0 |
Classification in consolidated balance sheet: |  |  |
Noncurrent asset | 0 | 0 |
Current liability | 0 | 0 |
Noncurrent liability | (240) | (238) |
Amounts included in AOCL: |  |  |
Net actuarial loss | 218 | 236 |
Prior service cost | 0 | 0 |
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax | $ 218 | $ 236 |
Assumptions used: |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate | 3.65% | 4.17% |
Discount rate used to calculate benefit obligation | 4.17% | 4.36% |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Rate of Compensation Increase | 4.58% | 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 Rate of Return on Plan Assets | 7.50% | 7.50% |
Other Postretirement Benefit Plans [Member] |  |  |
Benefit obligation: |  |  |
As of January 1 | $ 78 | $ 73 | 81
Fair value of plan assets: |  |  |
Service cost | 2 | 2 | 2
Interest cost on benefit obligation | 3 | 4 | 3
Participants’ contributions | 2 | 2 |
Actuarial loss (gain) | 3 | (11) |
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits | 1 | 0 |
Benefit payments | (6) | (5) |
Defined Benefit Plan, Plan Assets, Administration Expense | 0 | 0 |
As of January 1 | 33 | 30 | 30
Unfunded position as of December 31 | 45 | 43 |
Net actuarial loss (gain) included in comprehensive income | 0 | (10) |
Defined Benefit Plan, Amortization of Gain (Loss) | 0 | 0 | (1)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | (1) | (1)
Total Amounts included in comprehensive income | 0 | (11) |
Actual return on plan assets | 4 | 1 |
Company contributions | 3 | 2 |
Classification in consolidated balance sheet: |  |  |
Noncurrent asset | 0 | 0 |
Current liability | 0 | 0 |
Noncurrent liability | (45) | (43) |
Amounts included in AOCL: |  |  |
Net actuarial loss | (1) | (2) |
Prior service cost | 0 | 1 |
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax | $ (1) | $ (1) |
Assumptions used: |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Obligation, Discount Rate | 3.42% | 3.75% |
Defined Benefit Plan Discount rate - upper range | 3.70% | 4.23% |
Discount rate used to calculate benefit obligation | 3.75% | 3.90% |
Defined Benefit Plan Cost Discount rate - upper range | 4.23% | 4.45% |
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% | 6.26% |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets | 6.26% | 6.29% |
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, Benefit Obligation, Special and Contractual Termination Benefits | 0 | 0 |
Benefit payments | (2) | (2) |
Defined Benefit Plan, Plan Assets, Administration Expense | 0 | 0 |
As of January 1 | 17 | 16 | 15
Unfunded position as of December 31 | 10 | 11 |
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 | 0 | 0 |
Defined Benefit Plan, Accumulated Benefit Obligation | 27 | 27 |
Actual return on plan assets | 1 | 1 |
Company contributions | 2 | 2 |
Classification in consolidated balance sheet: |  |  |
Noncurrent asset | (17) | (16) |
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 | 3.65% | 4.17% |
Discount rate used to calculate benefit obligation | 4.17% | 4.36% |

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- Definition The interest rate used to adjust for the time value of money for the Defiend Benefit Plan Discount rate - upper range. + References No definition available. + Details
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- Definition The net increase or decrease of changes in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan.included in comprehensive income + References No definition available. + Details
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- Definition The amount of cash, securities, or other assets held by a third-party trustee pursuant to the terms of an agreement which assets are available to be used by beneficiaries to that agreement only within the specific terms thereof and which agreement is expected to terminate more than one year from the balance sheet date (or operating cycle, if longer) at which time the assets held-in-trust will be released or forfeited. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(b)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income from prior service cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of increase in benefit obligation for benefits provided to employees payable from defined benefit plan or payable upon retirement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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