RETIREMENT BENEFITS Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure
Defined Contribution Plan Employers Matching Contribution Percentage to Participants Percentage Conribution	100.00%
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 8
Defined Contribution Plan, Employer Matching Contribution, Percent	5.00%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Arising During Period, before Tax	$ 24
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.44%	3.75%
Other Postretirement Benefits Plan [Member] \| Fixed Income Securities
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	75.00%
Other Postretirement Benefits Plan [Member] \| Target 2020 Fund [Member]
Defined Benefit Plan Disclosure
Large Cap US Equitiies		32.00%
International Securities Funds		16.00%
Fixed Income Securities		52.00%
Other Postretirement Benefits Plan [Member] \| Target 2050 Fund [Member]
Defined Benefit Plan Disclosure
Large Cap US Equitiies		54.00%
Fixed Income Securities		10.00%
Cash Fund Investments		36.00%
Other Postretirement Benefits Plan [Member] \| Market index fund [Member]
Defined Benefit Plan Disclosure
Large Cap US Equitiies		100.00%
Other Postretirement Benefits Plan [Member] \| International index fund [Member]
Defined Benefit Plan Disclosure
Large Cap US Equitiies		4.00%
International Securities Funds		96.00%
Other Postretirement Benefits Plan [Member] \| U.S. bond index fund [Member]
Defined Benefit Plan Disclosure
Large Cap US Equitiies		23.00%
Other securities		8.00%
Fixed Income Securities		41.00%
Mortgage-backed securities		28.00%
Savings Plan [Member]
Defined Benefit Plan Disclosure
Defined Contribution Plan, Cost	$ 2
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure
Defined Contribution Plan, Employer Matching Contribution, Percent	3.00%
Company Contributions Vested	100.00%
Company Contributions Years	five
Defined Contribution Plan, Cost	$ 1
Minimum [Member] \| Other Postretirement Benefits Plan [Member] \| Equity Securities
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	25.00%
Minimum [Member] \| Other Postretirement Benefits Plan [Member] \| Fixed Income Securities
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	65.00%
Maximum [Member] \| Other Postretirement Benefits Plan [Member] \| Equity Securities
Defined Benefit Plan Disclosure
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	35.00%

Percentage of mutual fund that is invested in cash.

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Percentage company contributions are vested after five years.

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Number of years of continuous service when company contributions are fully vested.

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The percentage of the employer's matching contribution to a participants defined contribution plan as a matching contribution to the participants percentage contribution.

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Percentage of mutual fund that is invested in fixed income securities.

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- Definition

International Securities Funds

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- Definition

Percentage of mutual fund that is invested in large-cap U.S. equities.

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- Definition

Percent of mutual fund that is invested in mortgage-backed securities.

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- Definition

Percent of mutual fund that is invested in other securities.

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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Amount of cost for defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Amount, before tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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