Pension and Other Postretirement Benefits, Aggregate Accumulated Benefit Obligation in Excess of Fair Value (Details) - Pension Plans [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Aggregate accumulated benefit obligation (ABO)	$ 3,614	$ 3,831
Projected benefit obligation	3,681	3,875
Accumulated benefit obligation	3,367	3,490
Fair value of plan assets	$ 2,547	$ 2,651

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Amount of accumulated benefit obligation for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

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Amount of plan asset for defined benefit plan with accumulated benefit obligation in excess of plan assets.

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Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

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