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EMPLOYEE BENEFITS - Postretirement Benefits (Details) - USD ($) $ in Millions |  | 12 Months Ended
--- | --- | ---
Aug. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Profit Sharing Automatic Contribution By Employer, Percentage |  | 3.00% |  |
Decrease in postretirement benefit obligation | $ 76 |  |  |
Postretirement benefit plan re-measurement, net of tax | 29 |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |  |
Plan amendment | $ (76) |  |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
HRA credit inflation index for grandfathered retirees |  | 2.50% |  |
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract] |  |  |  |
Pension and Other Postretirement Benefits Cost (Reversal of Cost) |  | $ 164 | $ 120 | $ 84
Defined Contribution Plan, Cost |  | 13 | 18 | 12
Postretirement Benefits [Member] |  |  |  |
Decrease in postretirement benefit obligation |  |  | 34 |
Postretirement Benefits |  |  |  |
Service cost |  | 6 | 7 | 8
Interest cost |  | 7 | 8 | 10
Expected return on assets |  | (13) | (12) | (10)
Amortization of prior service credits |  | (10) | (7) | (7)
Amortization of unrecognized gains |  | (3) | (2) | 0
Net periodic (benefits) costs |  | (13) | (6) | 1
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |  |
Benefit obligation at beginning of year |  | 208 | 265 |
Service cost |  | 6 | 7 | 8
Interest cost |  | 7 | 8 | 10
Plan participants' contributions |  | 3 | 3 |
Actuarial (gains) |  | (26) | (34) |
Plan amendment |  |  | (34) |
Benefits paid |  | (9) | (9) |
Prescription drug rebates |  | 1 | 2 |
Benefit obligation at end of year |  | 190 | 208 | $ 265
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Prescription drug rebates |  | 1 | 2 |
Noncurrent postretirement benefit obligation |  | 14 | 19 |
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract] |  |  |  |
Prior service credit |  | 71 | 80 |
Unrecognized gains |  | 37 | 37 |
Deferred tax (liability) |  | (26) | (44) |
Net accumulated gains |  | $ 82 | $ 73 |
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract] |  |  |  |
Net unrecognized gains (losses), amortization period |  | 12 years 10 months 12 days |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |  |  |
Discount rate |  | 3.44% | 4.00% | 4.20%
Long-term rate of return on plan assets, net of tax |  | 7.13% | 7.13% | 6.65%
Pre age 65 |  | 6.56% | 6.81% | 7.00%
Post age 65 |  |  | 9.36% | 7.00%
Catastrophic drug benefit |  | 12.50% |  |
Ultimate healthcare cost trend rate |  | 4.50% | 4.50% | 4.50%
Year ultimate healthcare cost trend rate reached |  | 2026 | 2026 | 2026
HRA credit inflation index for grandfathered retirees |  | 2.50% |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Discount rate |  | 4.08% | 3.44% | 4.00%
Expected long-term rate of return on plan assets, net of tax |  | 7.13% | 7.13% | 7.13%
Pre age 65 |  | 6.31% | 6.56% | 6.81%
Post age 65 |  |  |  | 9.36%
Catastrophic drug benefit |  | 11.50% | 12.50% |
Ultimate healthcare cost trend rate |  | 4.50% | 4.50% | 4.50%
Year ultimate healthcare cost trend rate reached |  | 2026 | 2026 | 2026
HRA credit inflation index for grandfathered retirees |  | 2.50% | 2.50% |
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract] |  |  |  |
Estimated gross benefit payments, 2019 |  | $ 8 |  |
Estimated gross benefit payments, 2020 |  | 9 |  |
Estimated gross benefit payments, 2021 |  | 10 |  |
Estimated gross benefit payments, 2022 |  | 11 |  |
Estimated gross benefit payments, 2023 |  | 12 |  |
Estimated gross benefit payments, 2024-2028 |  | 66 |  |
Postretirement Benefits [Member] | Plan Assets [Member] |  |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |  |
Prescription drug rebates |  | 1 | $ 1 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Plan assets available for benefits at beginning of year |  | 189 | 164 |
Actual (losses) returns on plan assets |  | (8) | 29 |
Plan participants' contributions |  | 3 | 3 |
Benefits paid |  | (9) | (8) |
Prescription drug rebates |  | 1 | 1 |
Plan assets available for benefits at end of year |  | 176 | 189 | $ 164
Postretirement Benefits [Member] | Fidelity Spartan US Equity Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Plan assets available for benefits at beginning of year |  | 83 |  |
Plan assets available for benefits at end of year |  | 80 | 83 |
Postretirement Benefits [Member] | Vanguard 500 Index Fund [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Plan assets available for benefits at beginning of year |  | 104 |  |
Plan assets available for benefits at end of year |  | 93 | 104 |
Postretirement Benefits [Member] | Vanguard Total International Stock Member | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Plan assets available for benefits at beginning of year |  | 30 |  |
Plan assets available for benefits at end of year |  | 26 | 30 |
Postretirement Benefits [Member] | Total Registered Investment Companies [Member] |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Trust liabilities |  | (23) | (28) |
Postretirement Benefits [Member] | Total Registered Investment Companies [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |
Plan assets available for benefits at beginning of year |  | 217 |  |
Plan assets available for benefits at end of year |  | $ 199 | $ 217 |
Minimum [Member] |  |  |  |
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract] |  |  |  |
Profit Sharing Contribution Percentage |  | 8.00% |  |
Maximum [Member] |  |  |  |
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract] |  |  |  |
Profit Sharing Contribution Percentage |  | 18.00% |  |

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- Definition Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Health Care Cost Trend Rate Assumed For Next Fiscal Year, Post Age 65 + References No definition available. + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets 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 (h)(3) -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 increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new 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)(7) -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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