Employee Retirement Benefits - Net Periodic Income Cost Recognizedf for OCI (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Prior service benefit	$ 0	$ 0	$ 4
Net gains (losses)	(13)	37	(26)
Total	(13)	37	(22)
Tax effects on components of net periodic income (cost) recognized in OCI [Abstract]
Prior service benefit (cost)	0	0	3
Net gains (losses)	$ (4)	$ 23	$ (16)

Tax effects on components of net periodic income (cost) recognized in OCI [Abstract]

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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.

+ References

No definition available.

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Amount, after 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).

+ References

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- Definition

Amount, after tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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Amount of tax (expense) benefit for 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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